Get Air conditioning system Working with air conditioner service station -> 2.14 Checking pressures Guide for Volkswagen Sharan VAN Second Generation (2010-2023)

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Air conditioning systems with refrigeranR1234yf - General information - Edition 07.2017

Data sheefor R-cylinder if refrigeranis contaminated

Service contac

Dealership contact:

Email address:

Customer information:

Surname, firsname:

Street:

Town/city:

Vehicle model

Identification

Vehicle identification

number:

Mileage:

Gas analysis performed

on:

Information abouR-cylinder

Cylinder number:

Cylinder weighwith

contents:

(gross weight)

Fill volume

(neweight)

lk

Other comments

2.14

Checking pressures

⇒ “2.14.1 General information on checking pressures in the re‐

frigerancircuit”, page 170

⇒ “2.14.2 Pressures and temperatures in refrigerancircuit”, page

173

⇒ “2.14.3 Checking pressures in the refrigerancircuiwith the

ignition switched off”, page 176

⇒ “2.14.4 Checking pressures with air conditioning system switch‐

ed on - vehicles with mechanical air conditioning compressor”,

page 183 .

⇒ “2.14.5 Checking pressures with air conditioning system switch‐

ed on - vehicles with electrical air conditioning compressor”, page

205

2.14.1

General information on checking pres‐

sures in the refrigerancircui

Note

Work on the refrigerancircuithainvolves the air conditioner

service station can usually be carried ouwithouthe need to de-

energise the high-voltage system.

170

Rep. gr.87 - Air conditioning system

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Air conditioning systems with refrigeranR1234yf - General information - Edition 07.2017

Vehicles with electrically-actuated valves in the refrigerancircui

thaare noopen when de-energised:

lk

Note

On vehicles with high-voltage system and auxiliary air condition‐

ing system functions (“heapump mode” or “cooling of high-

voltage battery”), valves may be installed in the refrigerancircui

thaare noopen when de-energised. These valves are opened

and closed e.g. via incremental motors and are no longer actu‐

ated when the ignition is switched off. To check the pressures in

the refrigerancircuiwith the air conditioning system switched off,

however, no areas may be isolated, which is why these valves

musbe opened before work is carried ou⇒ Heating, air condi‐

tioning; Rep. gr. 87 ; Refrigerancircuit; System overview -

refrigerancircuiand ⇒ Vehicle diagnostic tester in “Guided Faul

Finding” mode.

– Use the vehicle diagnostic tester to open the electrically-ac‐

tuated valves thaare noopen when de-energised ⇒ Vehicle

diagnostic tester in “Guided FaulFinding” mode.

All vehicles

NOTICE

Risk of damage to the air conditioner compressor or air condi‐

tioner service station.

Opening the valves with the air conditioning system switched

on can cause a shorcircuibetween the high pressure and low

pressure side.

– Never open valves on the high pressure or low pressure side

with the air conditioning system switched on.

Note

♦ Certain conditions for testing are pertinento a certain vehicle

and are described in the vehicle-specific workshop manual ⇒

Heating, air conditioning; Rep. gr. 00 ; Repair instructions;

Checking cooling outpu.

♦ Check the cooling outpu⇒ Heating, air conditioning; Rep. gr.

00 ; Repair instructions; Checking cooling outpu(vehicle-spe‐

cific workshop manual).

♦ Connections with valve and service connections for measuring

and testing ⇒ Heating, air conditioning; Rep. gr. 87 ; Refrig‐

erancircuit; System overview - refrigerancircui(vehicle-

specific workshop manual)

♦ Depending on the version of air conditioner compressor, a

valve may be installed on the high-pressure side thaprevents

liquefied refrigeranflowing back into the air conditioner com‐

pressor after the air conditioning system is switched off. If an

air conditioner compressor with this valve is installed in a ve‐

hicle with a refrigerancircuiwith expansion valve, icould

take some time before the pressure on the high-pressure side

drops (the expansion valve is cold and the pressure on the

low-pressure side rises quickly after switching off, the expan‐

sion valve closes and refrigeranonly flows slowly on the low-

pressure side). If the air conditioner compressor is switched

on, the pressure on the low-pressure side drops, the expan‐

sion valve opens and refrigerancan flow on the low-pressure

side.

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Under certain operating conditions, residual moisture in the re‐

frigerancircuimay lead to the formation of ice athe air condi‐

tioner compressor regulating valve. The ice impairs the air

conditioner compressor control and causes the evaporator to be

cooled excessively and to ice up. Icing-up of the evaporator may

give rise to the following problems:

♦ Repeated or sporadic failure of the air conditioner (no cooling/

heaoutput) after a lengthy journey. After switching off the en‐

gine and waiting for a shorperiod, operation of air conditioner

returns to normal.

♦ Misting up of the windows on the inside after a long journey;

the windows are initially nocleared even by pressing the De-

frosbutton; the air conditioner functions properly again after

a shordelay following engine shut-off (or after switching off

the air conditioner).

Remedy:

– On vehicles with an air conditioner compressor with air con‐

ditioner compressor regulating valve - N280- , check the

measured value of the evaporator outputemperature sender

- G263- (via the “Read measured values” function). If the

measured value of the sender is too low under the operating

conditions described by the customer (aan ambientemper‐

ature above 0°C, colder than 0°C for an extended period even

though the -N280- is currently noactuated) or too high (higher

than approx. 10°C, even though the air conditioning system is

lk

functioning properly): the evaporator may ice up due to the

incorrecmeasured value ⇒ Vehicle diagnostic tester in “Gui‐

ded FaulFinding” mode - air conditioning system and ⇒

Heating, air conditioning; Rep. gr. 00 ; Repair instructions;

Checking cooling outpu(vehicle-specific workshop manual).

– On vehicles withouevaporator outputemperature sender -

G263- , use e.g. the footwell ventemperature sender - G192-

to check the outletemperature with the temperature seto

“low” or “cold” for the driver and fronpassenger side with the

lowessetting (4 or 5 bars) for the fresh air blower speed, air

outlein the footwell and fresh air mode under the operating

conditions described by the customer. If the measured value

of the sender is too low (with an ambientemperature higher

than 0°C, colder than 0°C for an extended period), the evap‐

orator could ice up due to the wrong measured value ⇒ Vehicle

diagnostic tester in “Guided FaulFinding” mode - air condi‐

tioning system.

– On vehicles with shut-off valves in the refrigerancircuit, check

the function and actuation of these valves ⇒ Vehicle diagnostic

tester in “Guided FaulFinding” mode - air conditioning sys‐

tem, ⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigeran

circuit; System overview - refrigerancircuiand ⇒ Heating,

air conditioning; Rep. gr. 00 ; Repair instructions; Checking

cooling outpu(vehicle-specific workshop manual).

– Check the refrigeranline from the evaporator (or from the in‐

ner heaexchanger) and the air conditioner compressor (thick

pipe, low pressure side) with the engine running. If this line is

very icy when the complainis encountered (a thin layer of ice

is acceptable), this is also evidence thathe temperature in the

evaporator is too low ⇒ Heating, air conditioning; Rep. gr. 87 ;

Refrigerancircuit; System overview - refrigerancircui(vehi‐

cle-specific workshop manual).

– Empty the refrigerancircuit, renew the receiver with dryer,

renew the reservoir with dryer or desiccancartridge and then

evacuate the refrigerancircuifor aleas3 hours ⇒ Heating,

air conditioning; Rep. gr. 87 ; Refrigerancircuit; System over‐

view - refrigerancircui(vehicle-specific workshop manual)

and ⇒ page 129 .

172

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Air conditioning systems with refrigeranR1234yf - General information - Edition 07.2017

♦ ⇒ “2.14.3 Checking pressures in the refrigerancircuiwith the

ignition switched off”, page 176

♦ ⇒ “2.14.4 Checking pressures with air conditioning system

switched on - vehicles with mechanical air conditioning com‐

pressor”, page 183 .

♦ ⇒ “2.14.5 Checking pressures with air conditioning system

switched on - vehicles with electrical air conditioning com‐

pressor”, page 205

2.14.2

Pressures and temperatures in refriger‐

ancircui

General information aboupressures and temperatures in the re‐

frigerancircui⇒ page 173

Pressures and temperatures in refrigerancircuiwith expansion

valve ⇒ page 174

General information aboupressures and temperatures in the re‐

frigerancircui

♦ The pressures and temperatures in the refrigerancircuide‐

pend on the currenoperating conditions (e.g. engine speed,

radiator running alevel 1, 2, or 3, engine temperature, air

conditioner compressor actuation on or off) as well as envi‐

ronmental influences (e.g. ambientemperature, humidity, re‐

quired cooling output).

♦ On vehicles with air conditioner compressor regulating valve -

N280- , the pressure on the low pressure side is varied by

means of -N280- actuation.

lk

♦ For these reasons, the values given in the following table may

only be considered guidelines. They occur aan engine speed

of 1,500 to 2,000 rpm and an ambientemperature of 20°C

after abou20 minutes.

♦ Refer to the vehicle-specific refrigerancircuifor the pressure

gauge semeasuremenconnections ⇒ Heating, air condi‐

tioning; Rep. gr. 87 ; Refrigerancircui(vehicle-specific work‐

shop manual).

♦ At 20°C and with the engine stationary, the refrigerancircui

will adjusitself to a pressure of 4.7 bar overpressure

⇒ “6.1.3 Vapour pressure table for refrigerant”, page 17 (va‐

pour pressure table).

Note

♦ Pressure is indicated in various units: 1 MPa (Mega-Pascal)

is equal to 10 bar or 145 psi; 1 bar absolute pressure is equal

to 0 bar, which is abouthe same as ambienpressure (at‐

mospheric pressure).

♦ The pressures and temperatures in refrigerancircuits with re‐

strictor and reservoir are abouthe same as those in refriger‐

ancircuits with expansion valve. Since Volkswagen/Audi

currently only installs refrigerancircuits with expansion valve,

justhis refrigerancircuiis described here.

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Air conditioning systems with refrigeranR1234yf - General information - Edition 07.2017

Pressures and temperatures in refrigerancircuiwith expansion

valve

Note

♦ The following log (p), h-diagram (logarithmic pressure, energy

diagram) shows the processes tharun during certain operat‐

ing conditions in the refrigerancircuit. These values change

depending on the environmental conditions (engine speed,

ambientemperature, requisite cooling output, etc.).

♦ The log (p), h-diagram shows the pressure (0 to 60 in bar ab‐

solute pressure) and the energy conten(100 to 420, specific

enthalpy in kilojoules per kg of R1234yf refrigerant) in the re‐

frigerancircuicycle.

lk

♦ The arrows indicate the direction of refrigeranflow in the re‐

frigerancircuit.

A - Area with vaporous refrigeran

B - Area with gaseous refrigeran

C - Area with liquefied refrigeran

D - Supercritical pressure and temperature range, physical state

of refrigeranundetermined (no longer a separation between liq‐

uefied and gaseous refrigerant)

1 - Low pressure side: outpuof inner heaexchanger, inpuof

air conditioner compressor, refrigeranis completely evapo‐

rated and gaseous, temperature of refrigeranis approx. -4°

C

2 - High pressure side: outpuof air conditioner compressor,

inpuof condenser, refrigeranhas been compressed and is

gaseous, temperature of refrigeranis up to approx. 80°C

3 - High pressure side: outpuof condenser (receiver), inpuof

inner heaexchanger, refrigeranhas been cooled down and

is liquefied, temperature of refrigeranis approx. 55°C

4 - High pressure side: outpuof inner heaexchanger, inpuof

expansion valve, liquefied refrigeranhas cooled down fur‐

ther, temperature of refrigeranis approx. 50°C

5 - Low pressure side: expansion valve on evaporator side, in‐

puof evaporator, liquefied refrigerancomes to resand

starts to evaporate, temperature of refrigeranapprox. -7°C

6 - Low pressure side: outpuof evaporator, expansion valve,

inpuof inner heaexchanger, refrigeranmainly evapora‐

ted, small percentage is still vaporous, temperature of re‐

frigeranapprox. -6°C

174

Rep. gr.87 - Air conditioning system

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Air conditioning systems with refrigeranR1234yf - General information - Edition 07.2017

Note

lk

♦ The temperatures given relate to the refrigeranin the refrig‐

erancircuit. The temperatures deviate from this on the sur‐

face of components containing refrigeranowing to hea

absorption and dissipation.

♦ The pressure and the temperature, too, are maintained aap‐

prox. 3 bar absolute pressure (equates to approx. 2 bar over‐

pressure) in refrigerancircuits with regulated air conditioner

compressor despite thermal changes and differenengine

speeds. This applies however only within the rated range of

the air conditioner compressor; if the rated range of the air

conditioner compressor is exceeded, the pressure will in‐

crease and so, too, will the temperature

⇒ “2.14 Checking pressures”, page 170 .

♦ On air conditioner compressors thado noregulate their per‐

formance themselves, the pressure on the low pressure side

and thereby the evaporator temperature are regulated by the

respective control via the air conditioner compressor regulat‐

ing valve - N280- . Depending on the version and the setting,

if an air temperature of less than approx. 2°C is measured after

the evaporator, the performance of the air conditioner com‐

pressor is lowered. Abelow 0°C, -N280- actuation is switched

off. This prevents the evaporator from cooling down too much

and becoming icy.

♦ On vehicles with two evaporators and two expansion valves,

the temperature and pressure in the refrigerancircuiare the

same athe second evaporator as those in vehicles with only

one evaporator and one expansion valve (parallel circuit).

♦ Depending on the version of refrigerancircuit, a componen

with inner heaexchanger may be installed. In the internal hea

exchanger, the holiquid refrigeranflowing on the high pres‐

sure side supplies energy to the cold gaseous or vaporous

refrigeranflowing on the low pressure side, thus enhancing

the efficiency of the air conditioner

⇒ “1.2.13 Refrigeranline with internal heaexchanger”, page

51 .

♦ Depending on the version of control uni(e.g. operating and

display unifor fronair conditioning system - E87- or Clima‐

tronic control uni- J255- ), the measured ambienconditions

(exterior temperature, moisture in the passenger compartmen

etc.) and the control unisetting (passenger compartmentem‐

perature, operating mode etc.), the pressure and thereby also

the temperature athe outpuof the evaporator can also be

regulated aa higher temperature ⇒ Vehicle diagnostic tester

in “Guided FaulFinding” mode - air conditioning system.

2. Working with air conditioner service station

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2.14.3

Checking pressures in the refrigeran

circuiwith the ignition switched off

Tesprerequisites ⇒ page 176

Checking pressures with the ignition switched off ⇒ page 179

Conditions for testing

Note

♦ Work on the refrigerancircuithainvolves the air conditioner

service station (checking the pressures in this case) can usu‐

ally be carried ouwithouthe need to de-energise the high-

voltage system.

♦ Only de-energise the high-voltage system if work on the high-

voltage system is necessary ⇒ page 3

All vehicles

Note

♦ Certain conditions for testing are pertinento a certain vehicle

and are described in the vehicle-specific workshop manual ⇒ ^lk

Heating, air conditioning; Rep. gr. 00 ; Repair instructions;

Checking cooling outpu(vehicle-specific workshop manual).

♦ Depending on the version of air conditioner compressor, a

valve may be installed on the high-pressure side thaprevents

liquefied refrigeranflowing back into the air conditioner com‐

pressor after the air conditioning system is switched off. If an

air conditioner compressor with this valve is installed in a ve‐

hicle with a refrigerancircuiwith expansion valve, icould

take some time before the pressure on the high-pressure side

drops (the expansion valve is cold and the pressure on the

low-pressure side rises quickly after switching off, the expan‐

sion valve closes and refrigeranonly flows slowly on the low-

pressure side). If the air conditioner compressor is switched

on, the pressure on the low-pressure side drops, the expan‐

sion valve opens and refrigerancan flow on the low-pressure

side.

♦ Check the cooling outpu⇒ Heating, air conditioning; Rep. gr.

00 ; Repair instructions; Checking cooling outpu(vehicle-spe‐

cific workshop manual).

♦ Connections with valve and service connections for measuring

and testing ⇒ Heating, air conditioning; Rep. gr. 87 ; Refrig‐

erancircui(vehicle-specific workshop manual).

♦ Connect the air conditioner service station

⇒ “2.2 Connecting air conditioner service station to refrigeran

circuit”, page 131 .

Under certain operating conditions, residual moisture in the re‐

frigerancircuimay lead to the formation of ice athe air condi‐

tioner compressor regulating valve. The ice impairs the air

conditioner compressor control and causes the evaporator to be

cooled excessively and to ice up. Icing-up of the evaporator may

give rise to the following problems:

♦ Repeated or sporadic failure of the air conditioner (no cooling/

heaoutput) after a lengthy journey. After switching off the en‐

gine and waiting for a shorperiod, operation of air conditioner

returns to normal.

176

Rep. gr.87 - Air conditioning system

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Air conditioning systems with refrigeranR1234yf - General information - Edition 07.2017

♦ Misting up of the windows on the inside after a long journey;

the windows are initially nocleared even by pressing the De-

frosbutton; the air conditioner functions properly again after

a shordelay following engine shut-off (or after switching off

the air conditioner).

Remedy:

– On vehicles with an air conditioner compressor with air con‐

ditioner compressor regulating valve - N280- ,_lkcheck the

measured value of the evaporator outputemperature sender

- G263- (via the “Read measured values” function). If the

measured value of the sender is too low under the operating

conditions described by the customer (aan ambientemper‐

ature above 0°C, colder than 0°C for an extended period even

though the -N280- is currently noactuated) or too high (higher

than approx. 10°C, even though the air conditioning system is

functioning properly): the evaporator may ice up due to incor‐

recactuation of -N280- or the incorrecmeasured value of -

G263- ⇒ Vehicle diagnostic tester in “Guided FaulFinding”

mode - air conditioning system and ⇒ Heating, air condition‐

ing; Rep. gr. 00 ; Repair instructions; Checking cooling outpu

(vehicle-specific workshop manual).

– On vehicles withouevaporator outputemperature sender -

G263- , use e.g. the footwell ventemperature sender - G192-

to check the outletemperature with the temperature seto

“low” or “cold” for the driver and fronpassenger side with the

lowessetting (4 or 5 bars) for the fresh air blower speed, air

outlein the footwell and fresh air mode under the operating

conditions described by the customer. If the measured value

of the sender is too low (with an ambientemperature higher

than 0°C, colder than 0°C for an extended period), the evap‐

orator could ice up due to the wrong measured value ⇒ Vehicle

diagnostic tester in “Guided FaulFinding” mode - air condi‐

tioning system.

– On vehicles with shut-off valves in the refrigerancircuit, check

the function and actuation of these valves ⇒ Vehicle diagnostic

tester in “Guided FaulFinding” mode - air conditioning system

⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerancircui

(vehicle-specific workshop manual) and ⇒ Heating, air con‐

ditioning; Rep. gr. 00 ; Repair instructions; Checking cooling

outpu(vehicle-specific workshop manual).

– Check the refrigeranline from the evaporator (or from the in‐

ner heaexchanger) and the air conditioner compressor (thick

pipe, low pressure side) with the engine running. If this line is

very icy when the complainis encountered (a thin layer of ice

is acceptable), this is also evidence thathe temperature in the

evaporator is too low ⇒ Heating, air conditioning; Rep. gr. 87 ;

Refrigerancircui(vehicle-specific workshop manual).

– Empty the refrigerancircuit, renew all reservoirs/receivers

with dryer or desiccancartridge and then evacuate the refrig‐

erancircuifor aleas3 hours ⇒ Heating, air conditioning;

Rep. gr. 87 ; Refrigerancircui(vehicle-specific workshop

manual) and

⇒ “2 Working with air conditioner service station”, page 129 .

Conditions for testing

♦ Observe the general information on checking pressures in the

refrigerancircui

⇒ “2.14.1 General information on checking pressures in the

refrigerancircuit”, page 170

2. Working with air conditioner service station

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Air conditioning systems with refrigeranR1234yf - General information - Edition 07.2017

Note

All of the conditions for testing marked with * are pertinento a

certain vehicle and are described in the vehicle-specific workshop

manual ⇒ Heating, air conditioning; Rep. gr. 00 ; Repair instruc‐

tions; Checking cooling outpu(vehicle-specific workshop man‐

ual).

General conditions for testing (these only have an influence on

the display of the pressure gauges during this measuremenwith

the air conditioning system switched on)

•

Radiator and condenser are clean (clean them if necessary).*

The heainsulation on the expansion valve is OK and properly

installed.*

•

The poly V-belis OK and properly tensioned. The belts for air

conditioner compressor and alternator are in good condition

and correctly tensioned.*

The drive unifor the air conditioner compressor is OK and

properly installed.*

•

All air ducts, covers and seals are OK and properly installed.*

Diagnosis of the air conditioning system finds no faults (with

the engine running and the air conditioning system switched

on), no compressor deactivation conditions are shown in the

measured values (only on vehicles with diagnosis “air condi‐

tioning system”).* ⇒ Vehicle diagnostic tester in “Guided Faul

Finding” mode of air conditioning system.

•

The air flow rate through the dusand pollen filter is noim‐

paired by dirt.*

All dash panel air vents are open.*

lk

Note

♦ Depending on the engine, the air conditioner compressor is

driven by differencomponents (belts or drive shaft). To pro‐

tecthese components and the engine, the pulley or the air

conditioner compressor drive uniis fitted with an overload

protection which is tripped if the air conditioner compressor is

nooperating smoothly ⇒ Heating, air conditioning; Rep. gr.

00 ; Repair instructions; Checking cooling outpu(vehicle-spe‐

cific workshop manual) and ⇒ Heating, air conditioning; Rep.

gr. 87 ; Air conditioner compressor (vehicle-specific workshop

manual).

♦ On certain versions, the radiator fan cuts in only after the pres‐

sure in the refrigerancircuihas exceeded a pre-sevalue

⇒ Vehicle diagnostic tester in “Guided FaulFinding” mode -

air conditioning system.

Other conditions for testing (these have an influence on the dis‐

play of the pressure gauge with this measurement)

•

The vehicle is noexposed to the sun's rays ⇒ Heating, air

conditioning; Rep. gr. 00 ; Repair instructions; Checking cool‐

ing outpu(vehicle-specific workshop manual).

•

Ambientemperature is above 15°C.

The ignition is switched off.

The air conditioner service station is connected to the refrig‐

erancircui

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Air conditioning systems with refrigeranR1234yf - General information - Edition 07.2017

⇒ “2.2 Connecting air conditioner service station to refrigeran

circuit”, page 131 .

♦ ⇒ “2.14.4 Checking pressures with air conditioning system

switched on - vehicles with mechanical air conditioning com‐

pressor”, page 183 .

lk

♦ ⇒ “2.14.5 Checking pressures with air conditioning system

switched on - vehicles with electrical air conditioning com‐

pressor”, page 205

Checking pressures with the ignition switched off

Note

♦ The switching pressures for actuation of the air conditioner

compressor regulating valve - N280- , the air conditioning sys‐

tem magnetic clutch - N25- (if fitted) and the radiator fan (e.g.

radiator fan - V7- / radiator fan 2 - V177- ) are vehicle-specific

⇒ Vehicle diagnostic tester in “Guided FaulFinding” mode -

air conditioning system.

♦ The pressures musbe measured athe service connections;

the fitting locations of these connections are vehicle-specific

⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerancircui

(vehicle-specific workshop manual).

♦ Once the planned measures are complete, separate the air

conditioner service station from the refrigerancircuiand

switch ioff

⇒ “2.8 Switching off air conditioner service station and sepa‐

rating from refrigerancircuit”, page 151 .

•

The engine is aoperating temperature (aan ambientem‐

perature less than 25°C).

Note

♦ Should the engine nobe aoperating temperature, take the

vehicle for a shordrive.

♦ To testhe cooling output, the engine does nohave to be a

operating temperature. However, to demand a certain cooling

outpufrom the air conditioning system aan ambientemper‐

ature of less than 25°C, the engine is required to be warm if

ambientemperatures are low.

♦ Observe the tesprerequisites ⇒ page 176 .

– On vehicles with high-voltage system, switch off “stationary air

conditioning” function (deactivate)⇒ Owner's Manual and ⇒

Operating instructions of infotainmen/ MMI .

– Switch off ignition.

– Connect the air conditioner service station

⇒ “2.2 Connecting air conditioner service station to refrigeran

circuit”, page 131 .

– Check the pressures in the refrigerancircuiwith the engine

stationary.

– Take pressure readings from pressure gauges of air condi‐

tioner service station . Two results may be displayed:

♦ The pressure in the refrigerancircuiis lower than indicated

in the following table ⇒ page 182 .

♦ The pressure in the refrigerancircuiis equal to or greater than

thain the following table ⇒ page 183 .

2. Working with air conditioner service station

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Air conditioning systems with refrigeranR1234yf - General information - Edition 07.2017

Note

♦ Vapour pressure table for R1234yf refrigeran

⇒ “6.1.3 Vapour pressure table for refrigerant”, page 17

♦ On vehicles with high-voltage system and auxiliary air condi‐

tioning system functions (“heapump mode” or “cooling of

high-voltage battery”), valves may be installed in the refriger‐

ancircuithaare noopen when de-energised. These valves

are opened and closed e.g. via incremental motors and are no

longer actuated when the ignition is switched off. Depending

lk

on the lasoperating status of the air conditioning system, cer‐

tain areas of the refrigerancircuicould be isolated by these

valves. Depending on the layouof the service connections in

the refrigerancircuit, these could be in an area thais isolated

(e.g. the area with the service connection on the high pressure

side). If necessary, these valves musbe opened before the

pressure is tested ⇒ Heating, air conditioning; Rep. gr. 87 ;

Refrigerancircui(vehicle-specific workshop manual) and

⇒ Vehicle diagnostic tester in “Guided FaulFinding” mode.

♦ The pressures given in the table are slightly lower than speci‐

fied in the vapour pressure table for the R1234yf refrigerant.

The evaporation pressure of the refrigeranin the refrigeran

circuiis orientated around the coldescomponenand could

therefore also be slightly lower in a correctly charged refriger‐

ancircuithan thaspecified for the R1234yf refrigeranin the

vapour pressure table.

Ambientemperature (in de‐ Pressure in the refrigerancir‐

grees C)

+15 °C

+20 °C

+25 °C

+30 °C

+35 °C

+40 °C

+45 °C

cuiin bar positive pressure

3.5

4.4

5.3

6.3

7.4

8.6

10.0

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Note

♦ The temperature of the components of the refrigerancircui

should be the same as the ambientemperature. If individual

components of the refrigerancircuiare warmer or colder, the

pressure will deviate from the values shown in the tables.

♦ Absolute pressure means tha0 bar corresponds to an abso‐

lute vacuum. The normal ambienpressure corresponds to 1

bar absolute pressure. On mospressure gauges, a reading

of 0 bar corresponds to an absolute pressure of one bar (which

is confirmed by the existence of a -1 bar marking beneath the

0 scale marking).

♦ On vehicles with pressure senders ( high pressure sender -

G65- , pressure sender for refrigerancircui- G805- or refrig‐

eranpressure and temperature sender - G395- , etc.) for

which the measured pressure is displayed in the measured

values of the diagnosis, the measured pressure should corre‐

late with the values in the table (or be slightly higher) ⇒ Vehicle

diagnostic tester in “Guided FaulFinding” mode - air condi‐

tioning system and ⇒ Heating, air conditioning; Rep. gr. 00 ;

Repair instructions; Checking cooling outpu(vehicle-specific

workshop manual).

lk

♦ The pressure is given in differenunits, 1 MPa (megapascal)

equates to 10 bar overpressure or 145 psi. A0 bar overpres‐

sure, 1 bar absolute pressure is approximately the same as

ambienpressure (atmospheric pressure).

If the measured values are OK and there is no complaint:

– Unscrew (close) the handwheels of the quick-release coupling

adapters ⇒ Operating instructions air conditioner service sta‐

tion .

– Extract the refrigeranfrom the two charge hoses using the air

conditioner service station as instructed in the relevanoper‐

ating manual ⇒ Operating instructions air conditioner service

station .

– Switch off the air conditioner service station (and isolate ifrom

the power supply if necessary)

⇒ “2.8 Switching off air conditioner service station and sepa‐

rating from refrigerancircuit”, page 151 .

If the measured values are OK and there is complaint:

– Check the cooling outpuof the air conditioning system ⇒

Heating, air conditioning; Rep. gr. 00 ; Repair instructions;

Checking cooling outpu(vehicle-specific workshop manual)

and watch the pressures in the refrigerancircuit.

♦ ⇒ “2.14.4 Checking pressures with air conditioning system

switched on - vehicles with mechanical air conditioning com‐

pressor”, page 183 .

♦ ⇒ “2.14.5 Checking pressures with air conditioning system

switched on - vehicles with electrical air conditioning com‐

pressor”, page 205

If the measured values are noOK:

– Investigate the cause of the deviation and rectify.

2. Working with air conditioner service station

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Note

♦ If the pressures are too low, icould be because there is too

little refrigeranin the circui⇒ Heating, air conditioning; Rep.

gr. 00 ; Technical data (vehicle-specific workshop manual)

and ⇒ “2.4 Emptying refrigerancircuit”, page 137 .

♦ If the pressures are too high, there may be too much refriger‐

anor refrigeranoil in the circuit. Empty the refrigerancircui

using the air conditioner service station

⇒ “2.4 Emptying refrigerancircuit”, page 137 . If the extracted

refrigeranvolume is greater than the specified fill capacity for

the R1234yf refrigeran⇒ Heating, air conditioning; Rep. gr.

00 ; Technical data (vehicle-specific workshop manual), evac‐

uate the refrigerancircuiand recharge with the correc

amounof R1234yf refrigerant. Then repeathe test. If the ex‐

tracted quantity of refrigeranroughly equates to the specified

fill capacity for the R1234yf refrigeranor is less, clean the re‐

frigerancircuiwith refrigeran

lk

⇒ “1.6 Cleaning refrigerancircuit”, page 92 . Then add the

specified amounof refrigeranoil, evacuate the refrigeran

circuit, recharge with the correcvolume of R1234yf refrigeran

and repeathe test.

♦ If the pressures are too low or too high and contaminated re‐

frigeranis found during the gas analysis, this may be the

cause of the deviation (differenrefrigerants have varying va‐

pour pressures). Empty the refrigerancircuiand then clean

with R1234yf refrigeran

⇒ “2.3 Performing gas analysis of refrigerant”, page 134 ,

⇒ “2.4 Emptying refrigerancircuit”, page 137 and

⇒ “1.6 Cleaning refrigerancircuit”, page 92

The pressure in the refrigerancircuiis lower than indicated in

the table

Too little refrigeranin circuit.

– Check for leaks in the refrigerancircui

⇒ “1.4 Investigating leaks”, page 68 .

– Check the high pressure safety valve

⇒ “1.2.17 High-pressure safety valve”, page 53 .

If the high pressure safety valve has blown (check

⇒ “1.2.17 High-pressure safety valve”, page 53 ):

– Check radiator fan actuation or the radiator fan ⇒ Vehicle di‐

agnostic tester in “Guided FaulFinding” mode - air condition‐

ing system.

– On vehicles with shut-off valves for the refrigerancircuit,

check the actuation and function of these shut-off valves ⇒ Ve‐

hicle diagnostic tester in “Guided FaulFinding” mode - air

conditioning system (and battery control) and ⇒ Heating, air

conditioning; Rep. gr. 87 ; Refrigerancircui(vehicle-specific

workshop manual).

– Check refrigeranlines and refrigeranhoses for signs of

crushing (bottle-neck), external damage and tighbends ⇒

Heating, air conditioning; Rep. gr. 87 ; Refrigerancircui(ve‐

hicle-specific workshop manual) and ⇒ Heating, air condi‐

tioning; Rep. gr. 87 ; Refrigerancircui(vehicle-specific

workshop manual).

– If no faulcan be detected, clean the refrigerancircui

⇒ “1.6 Cleaning refrigerancircuit”, page 92 .

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The pressure in the refrigerancircuiis equal to or greater than

thain the table

♦ ⇒ “2.14.4 Checking pressures with air conditioning system

switched on - vehicles with mechanical air conditioning com‐

pressor”, page 183 .

♦ ⇒ “2.14.5 Checking pressures with air conditioning system

switched on - vehicles with electrical air conditioning com‐

pressor”, page 205

2.14.4

Checking pressures with air condition‐

ing system switched on - vehicles with

mechanical air conditioning compressor

lk

Checking pressures ⇒ page 183

Specifications for pressures in the refrigerancircui

⇒ page 187

Checking pressures

Refrigerancircuiwith expansion valve, receiver with or withou

air conditioning system magnetic clutch - N25- and air conditioner

compressor regulating valve - N280- (with externally regulated air

conditioner compressor)

Note

♦ Connecthe air conditioner service station

⇒ “2.2 Connecting air conditioner service station to refrigeran

circuit”, page 131 .

♦ If on vehicles with two evaporators a problem is encountered

in jusone evaporator, check the pressures in the refrigeran

circuit. If these are OK, check the line connection between the

evaporator thais causing the problem and the outleof the

line connection athe distribution poinof the refrigeranlines

(for bottle-neck or blockage). If no faulcan be determined,

empty the refrigerancircuiand recharge with the prescribed

amounof refrigerant. Then check the pressures and the cool‐

ing outpuof the air conditioner again. If the problem persists,

replace the expansion valve upstream of the problematic

evaporator ⇒ Heating, air conditioning; Rep. gr. 87 ; Refrig‐

erancircui(vehicle-specific workshop manual).

♦ ⇒ “2.14.3 Checking pressures in the refrigerancircuiwith the

ignition switched off”, page 176

Conditions for testing

•

The air conditioner service station is connected to the refrig‐

erancircui

⇒ “2.2 Connecting air conditioner service station to refrigeran

circuit”, page 131 .

•

Observe the conditions for testing pressures in the refrigeran

circuiwith the ignition switched off ⇒ page 176 .

The pressures in the refrigerancircuicomply with the speci‐

fications with the ignition switched off

⇒ “2.14.3 Checking pressures in the refrigerancircuiwith the

ignition switched off”, page 176 .

•

Observe the conditions for testing the cooling outpu⇒ Heat‐

ing, air conditioning; Rep. gr. 00 ; Repair instructions; Check‐

ing cooling outpu(vehicle-specific workshop manual).

2. Working with air conditioner service station

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Air conditioning systems with refrigeranR1234yf - General information - Edition 07.2017

Note

♦ The switching pressures for actuation of the air conditioner

compressor regulating valve - N280- , the air conditioning sys‐

tem magnetic clutch - N25- (if fitted) and the radiator fan - V7-

are vehicle-specific ⇒ Vehicle diagnostic tester in “Guided

FaulFinding” mode - air conditioning system.

♦ The pressures musbe measured athe service connections;

the fitting locations of these connections are vehicle-specific

⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerancircui

(vehicle-specific workshop manual).

•

The engine is aoperating temperature (aan ambientem‐

perature less than 25°C).

Note

♦ Should the engine nobe aoperating temperature, take the

vehicle for a shordrive.

♦ To testhe cooling output, the engine does nohave to be a

operating temperature. However, to demand a certain cooling

outpufrom the air conditioning system aan ambientemper‐

ature of less than 25°C, the engine is required to be warm if

ambientemperatures are low.

lk

– Start engine.

– Set the air conditioning system to maximum cooling outpu⇒

Heating, air conditioning; Rep. gr. 00 ; Repair instructions;

Checking cooling outpu(vehicle-specific workshop manual).

•

The air conditioner compressor is actually driven with the en‐

gine running (visual check ⇒ Heating, air conditioning; Rep.

gr. 87 ; Refrigerancircui(vehicle-specific workshop man‐

ual)).

•

The air conditioner compressor regulating valve - N280- is ac‐

tuated ⇒ Vehicle diagnostic tester in “Guided FaulFinding”

mode - air conditioning system.

Note

♦ Depending on the engine, the air conditioner compressor is

driven by differencomponents (belts or drive shaft). To pro‐

tecthese components and the engine, the pulley or the air

conditioner compressor drive uniis fitted with an overload

protection which is tripped if the air conditioner compressor is

nooperating smoothly ⇒ Heating, air conditioning; Rep. gr.

87 ; Air conditioner compressor (vehicle-specific workshop

manual).

♦ On vehicles with air conditioner compressor regulating valve -

N280- , the control currencan be gleaned from the measured

values ⇒ Vehicle diagnostic tester in “Guided FaulFinding”

mode - air conditioning system.

If the air conditioner compressor is nodriven or the regulating

valve noactivated when the engine is running:

– Determine the cause, e.g. by interrogating the evenmemory

of the air conditioning system, and rectify i⇒ Vehicle diag‐

nostic tester in “Guided FaulFinding” mode - air conditioning

system.

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– If fitted, check the voltage supply for the air conditioning sys‐

tem magnetic clutch - N25- . If this is OK, repair the magnetic

clutch ⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigeran

circui(vehicle-specific workshop manual).

– Check actuation of the air conditioner compressor regulating

valve - N280- ⇒ Vehicle diagnostic tester in “Guided Faul

Finding” mode - air conditioning system.

lk

Note

♦ On air conditioner compressors with an air conditioning sys‐

tem magnetic clutch - N25- , the air conditioner compressor

only works (delivers refrigerant) if in addition to the air condi‐

tioner compressor regulating valve - N280- , -N25- is actuated

⇒ Vehicle diagnostic tester in “Guided FaulFinding” mode -

air conditioning system.

♦ -N280- (and -N25- ) is actuated by the air conditioning system

control uni- J301- , the operating and display unifor fronair

conditioning system - E87- and the Climatronic control uni-

J255- or a downstream control uni⇒ Vehicle diagnostic tester

in “Guided FaulFinding” mode - air conditioning system and

⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerancircui

(vehicle-specific workshop manual).

♦ All of the conditions for testing marked with * are pertinento

a certain vehicle and are described in the vehicle-specific

workshop manual ⇒ Heating, air conditioning; Rep. gr. 00 ;

Repair instructions (vehicle-specific workshop manual) and ⇒

Heating, air conditioning; Rep. gr. 87 ; Refrigerancircui(ve‐

hicle-specific workshop manual).

•

The radiator and condenser are clean (clean if necessary) * ⇒

Heating, air conditioning; Rep. gr. 87 ; Refrigerancircui(ve‐

hicle-specific workshop manual).

The heainsulation on the expansion valve is OK and mounted

correctly * ⇒ Heating, air conditioning; Rep. gr. 87 ; Refrig‐

erancircui(vehicle-specific workshop manual).

The poly V-belis OK and properly tensioned. The belts for air

conditioner compressor and alternator are in good condition

and correctly tensioned.* ⇒ Heating, air conditioning system;

Rep. gr. 87 ; Air conditioner compressor (vehicle-specific

workshop manual) and ⇒ Heating, air conditioning system;

Rep. gr. 87 ; Refrigerancircui(vehicle-specific workshop

manual).

•

The drive unifor the air conditioner compressor is OK and

mounted properly * ⇒ Heating, air conditioning; Rep. gr. 87 ;

Refrigerancircui(vehicle-specific workshop manual) and ⇒

Heating, air conditioning; Rep. gr. 87 ; Air conditioner com‐

pressor (vehicle-specific workshop manual).

•

The air ducts, covers and seals are OK and mounted correctly

* ⇒ Heating, air conditioning; Rep. gr. 87 ; Overview of fitting

locations - air conditioning system (vehicle-specific workshop

manual).

Diagnosis of the air conditioning system finds no faults (with

the engine running and the air conditioning system switched

on), no compressor deactivation conditions are shown in the

measured values of the respective control uni(only on vehi‐

cles with diagnosis “air conditioning system”).* ⇒ Vehicle di‐

agnostic tester in “Guided FaulFinding” mode of air

conditioning system.

•

The air flow rate through the dusand pollen filter is noim‐

paired by dirt.* ⇒ Heating, air conditioning system; Rep. gr.

2. Working with air conditioner service station

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87 ; Overview of fitting locations - air conditioning system (ve‐

hicle-specific workshop manual).

•

The heater and air conditioner does nodraw any secondary

air ahighesfresh air blower speed. The evaporator and heat‐

er are nodrawing in secondary air athe highesfresh air

lk

blower speed * ⇒ Heating, air conditioning; Rep. gr. 87 ;

Overview of fitting locations - air conditioning system (vehicle-

specific workshop manual).

The air flaps in the heating and air conditioning unit, in the

heating and in the evaporator reach their end position * ⇒

Heating, air conditioning; Rep. gr. 00 ; Repair instructions;

Checking cooling outpu(vehicle-specific workshop manual)

and ⇒ Heating, air conditioning; Rep. gr. 87 ; Overview of

fitting locations - air conditioning system (vehicle-specific

workshop manual).

•

The fresh air intake ducts under the bonneand in the pas‐

senger compartmenand the corresponding water drain

valves are OK * ⇒ Heating, air conditioning; Rep. gr. 00 ;

Repair instructions; Checking cooling outpu(vehicle-specific

workshop manual) and ⇒ Heating, air conditioning; Rep. gr.

87 ; Overview of fitting locations - air conditioning system (ve‐

hicle-specific workshop manual).

•

Engine warm.

The vehicle is noexposed to the sun's rays ⇒ Heating, air

conditioning; Rep. gr. 00 ; Repair instructions; Checking cool‐

ing outpu(vehicle-specific workshop manual).

•

Ambientemperature is above 15°C.

All dash panel diffusers are open * ⇒ Heating, air conditioning;

Rep. gr. 87 ; Air ducsystem (vehicle-specific workshop man‐

ual).

Setting e.g. on operating and display unifor fronair conditioning

system - E87- and Climatronic control uni- J255- or air condi‐

tioning system control uni- J301- (and operating and display uni

for rear Climatronic - E265- on vehicles with two heating and air

conditioning units) * ⇒ Heating, air conditioning; Rep. gr. 00 ;

Repair instructions; Checking cooling outpu(vehicle-specific

workshop manual) and ⇒ Heating, air conditioning; Rep. gr. 87 ;

Overview of fitting locations - air conditioning system (vehicle-

specific workshop manual).

Setting on -E87- / -J255- *: ⇒ Heating, air conditioning; Rep. gr.

00 ; Repair instructions; Checking cooling outpu(vehicle-specific

workshop manual) and ⇒ Heating, air conditioning; Rep. gr. 87 ;

Overview of fitting locations - air conditioning system (vehicle-

specific workshop manual).

– Select “Auto” mode (air conditioner compressor switched on).

– Set temperature to “cold” or “LO” for the driver and fronpas‐

senger side (and the rear on the lefand righin vehicles with

two heating and air conditioning units).

Setting on -J301- *:

– Press A/C button and Rec or recirculate buttons.

– Turn rotary temperature knob in direction of “cold” stop.

– Set rotary fresh air blower switch to “4” (maximum fresh air

blower speed).

The following conditions for testing should then be mein the sys‐

tem:

•

The radiator fan - V7- is running or the radiator fan - V7- and

radiator fan 2 - V177- are running (aleasstage 1) * ⇒ Heat‐

ing, air conditioning; Rep. gr. 00 ; Repair instructions; Check‐

186

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Air conditioning systems with refrigeranR1234yf - General information - Edition 07.2017

ing cooling outpu(vehicle-specific workshop manual) and ⇒

Heating, air conditioning; Rep. gr. 87 ; Overview of fitting lo‐

cations - air conditioning system (vehicle-specific workshop

manual).

Note

On certain versions, the radiator fan cuts in only after the pressure

in the refrigerancircuihas exceeded a pre-sevalue ⇒ Vehicle

diagnostic tester in “Guided FaulFinding” mode - air conditioning

system.

lk

•

The fresh air blower - V2- (and the rear fresh air blower - V80-

on vehicles with two heating and air conditioning units) is

running amaximum speed.*

•

The coolanshut-off valve is closed * ⇒ Heating, air condi‐

tioning; Rep. gr. 00 ; Repair instructions; Checking cooling

outpu(vehicle-specific workshop manual) and ⇒ Heating, air

conditioning; Rep. gr. 87 ; Overview of fitting locations - air

conditioning system (vehicle-specific workshop manual).

•

The valves of the pump-valve uniare closed and the coolan

circulation pump is nodelivering * ⇒ Heating, air conditioning;

Rep. gr. 00 ; Repair instructions; Checking cooling outpu

(vehicle-specific workshop manual) and ⇒ Heating, air con‐

ditioning; Rep. gr. 87 ; Overview of fitting locations - air

conditioning system (vehicle-specific workshop manual).

•

The fresh air blower - V2- (and the rear fresh air blower - V80-

on vehicles with two heating and air conditioning units) is

running amaximum speed.*

The air recirculation flap/fresh air flap is in “recirculation

mode” (within 1 minute after starting the vehicle, the air flow

flap closes and the air recirculation flap opens).*

•

The coolanshut-off valve is closed.*

The valves for the pump-valve uniare closed and the coolan

circulation pump is nodelivering.*

Specifications for pressures in the refrigerancircui

♦ Observe the conditions for testing and the pressures

⇒ page 183 .

Testing:

– Raise engine speed to 2000 rpm.

– Observe pressure display (e.g. pressure gauge) of air condi‐

tioner service station ⇒ Operating instructions of air condi‐

tioner service station .

Note

♦ The switching pressures for actuation of the air conditioner

compressor regulating valve - N280- and the radiator fan are

vehicle-specific ⇒ Vehicle diagnostic tester in “Guided Faul

Finding” mode - air conditioning system.

♦ The pressures musbe measured athe service connections;

the fitting locations of these connections are vehicle-specific

⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerancircui

(vehicle-specific workshop manual).

2. Working with air conditioner service station

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High-pressure side:

Rising from starting pressure (when pressure gauge is connec‐

ted) to maximum 20 bar.

Low-pressure side:

From the outpupressure (when connecting the pressure gauge)

dropping to a value of between 1.5 and 2.3 bar absolute pressure

(depending on required cooling output).

lk

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lk

Note

♦ In the evenof a very high cooling outpu(e.g. ahigh outside

temperatures and high fresh air blower speed while the engine

is running slowly), the air conditioner compressor is initially

incapable of changing the pressure on the low pressure side

to the specified level (e.g. for a certain period after switching

on the air conditioning system). The air conditioner compres‐

sor is actuated with the maximum specified control current.

However, the delivery volume of the air conditioner compres‐

sor is noenough under these operating conditions and athis

engine speed to lower the pressure on the low pressure side

to the specification. One way of checking the regulating be‐

haviour of the air conditioner compressor under these condi‐

tions is to actuate e.g. the fresh air blower with only approx.

40% of the maximum voltage and to check the pressures a

reduced fresh air blower speed ⇒ Vehicle diagnostic tester in

“Guided FaulFinding” mode - air conditioning system and ⇒

Heating, air conditioning; Rep. gr. 00 ; Repair information;

Checking cooling outpu(vehicle-specific workshop manual).

♦ If the demand on the cooling outpuis low (e.g. aan ambien

temperature of 20°C and a low fresh air blower speed), pres‐

sure on the high pressure side may only increase up to a value

of 6 to 7 bar (the energy exchange is low, the refrigeranis

cooled down quickly in the condenser). To check the regulat‐

ing behaviour and the pressures in the refrigerancircuiunder

these conditions, e.g. actuate the fresh air blower with maxi‐

mum voltage, sethe air conditioning system to maximum

heating outpuand activate air recirculation ⇒ Vehicle diag‐

nostic tester in “Guided FaulFinding” mode - air conditioning

system and ⇒ Heating, air conditioning; Rep. gr. 00 ; Repair

instructions; Checking cooling outpu(vehicle-specific work‐

shop manual).

♦ Under unfavourable conditions (very high ambientempera‐

tures, high atmospheric humidity), the pressure on the high

pressure side can increase to a maximum of 29 bar.

♦ The specified working currenfor the air conditioner compres‐

sor regulating valve - N280- is displayed as a measured value

by the operating and display unifor fronair conditioning sys‐

tem - E87- , the air conditioning system control uni- J301- and

the Climatronic control uni- J255- ⇒ Vehicle diagnostic tester

in “Guided FaulFinding” mode - air conditioning system.

♦ The high pressure measured by the high pressure sender -

G65- , the pressure sender for refrigerancircui- G805- and

the refrigeranpressure and temperature sender - G395- is

displayed as a measured value by -E87- , -J301- or -J255-

⇒ Vehicle diagnostic tester in “Guided FaulFinding” mode -

air conditioning system.

♦ The low pressure adjusts depending on the control currenfor

the air conditioner compressor regulating valve - N280- and

the control characteristic of the expansion valve within the

performance band of the air conditioner compressor in the tol‐

erance range ⇒ Vehicle diagnostic tester in “Guided Faul

Finding” mode - air conditioning system.

♦ In unfavourable conditions (very high ambientemperatures,

high air humidity), the performance of the air conditioner com‐

pressor may noalways be enough to reach the specified

pressure value within the given time (icould take slightly lon‐

ger, depending on the engine speed, for the prescribed low

pressure to be reached).

2. Working with air conditioner service station

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♦ If the air conditioner compressor's capacity utilisation is above

90%, pressure on the low pressure side could be higher than

the specified tolerance range. The air conditioner compressor

outpuis no longer sufficienin the prevailing conditions (am‐

bientemperature, air humidity, setting of the air conditioning

system, engine speed, etc.) to change the pressure on the low

pressure side to approx. 2 bar.

♦ The specified working currenfor the air conditioner compres‐

sor regulating valve - N280- musbe higher than 0.3 A so tha

-N280- can be actuated reliably ⇒ Vehicle diagnostic tester in

“Guided FaulFinding” mode - air conditioning system.

♦ When setting to “maximum cooling output”, the control curren

for the air conditioner compressor regulating valve - N280- is

regulated aapprox. 0.65 A (to 0.85 A). This measured value

is vehicle-specific and is displayed in the ⇒ Vehicle diagnostic

tester in “Guided FaulFinding” mode - air conditioning sys‐

tem.

♦ Absolute pressure means tha0 bar corresponds to an abso‐

lute vacuum. The normal ambienpressure corresponds to 1

bar absolute. On mospressure gauges, a reading of 0 bar

corresponds to an absolute pressure of 1 bar (which is con‐

firmed by the existence of a -1 bar marking beneath the 0 scale

marking). Depending on the respective control universion,

pressure can be displayed as a measured value based on ab‐

solute or relative pressure (difference between displays 1 bar)

⇒ Vehicle diagnostic tester in “Guided FaulFinding” mode -

air conditioning system and ⇒ Heating, air conditioning; Rep.

gr. 00 ; Repair instructions; Checking cooling outpu(vehicle-

specific workshop manual).

♦ The temperature of the air after the evaporator, the currenair

conditioner compressor speed and the pressure of the refrig‐

eranon the high pressure side along with the specified work‐

ing currenfor the air conditioner compressor regulating valve

- N280- are displayed e.g. as a measured value by the oper‐

ating and display unit, the Climatronic control uni- J255-

⇒ Vehicle diagnostic tester in “Guided FaulFinding” mode -

air conditioning system.

Possible deviations from specification,

cause and rectification

♦ The required cooling outpuis no

reached.

⇒ page 192

♦ High pressure remains constanor in‐

creases only slightly (above the pressure

measured when the engine is station‐

ary).

♦ Low pressure drops quickly to the spec‐

ification or lower.

♦ The required cooling outpuis no

reached.

⇒ page 193

♦ The high pressure equates to the speci‐

fication

♦ The low pressure equates to the specifi‐

cation or is too low

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Possible deviations from specification,

cause and rectification

♦ The requisite cooling outpuis no

reached.

⇒ page 194

⇒ page 195

♦ High pressure does noincrease or only

marginally above the pressure with the

engine stationary

♦ The low pressure does nodrop or only

marginally

♦ The requisite cooling outpuis no

reached.

♦ The high pressure increases beyond the

specified value

♦ Low pressure drops quickly to the spec‐

ification or lower.

♦ The requisite cooling outpuis reached ⇒ page 196

initially buafter a while or after an ex‐

tended period, the cooling outpuis no

longer sufficient.

lk

♦ The high pressure and the low pressure

are normal to starwith

♦ After some time, the high pressure rises

above the specification, the low pressure

still equates to the specification or i

drops below the specification.

♦ The requisite cooling outpuis reached ⇒ page 198

initially buafter a shoror extended pe‐

riod, the required level is no longer

reached.

♦ The high pressure and low pressure are

normal to starwith buafter a while, the

high pressure rises above the specifica‐

tion and the low pressure drops to the

specification or lower.

♦ The high pressure and low pressure are

normal to starwith. After a while, the low

pressure drops to the specification or

lower and the evaporator ices up.

♦ The requisite cooling outpuis reached. ⇒ page 199

♦ The high pressure equates to the speci‐

fication

♦ The low pressure is too low (lower than

the specification)

♦ The air conditioner compressor is noisy ⇒ page 201

(especially immediately after being

switched on),

♦ The requisite cooling outpuis reached.

♦ High pressure normal or too high

♦ The low pressure is normal or too high

(the specification is noalways reached)

2. Working with air conditioner service station

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Possible deviations from specification,

cause and rectification

lk

♦ The required cooling outpuis no

reached.

⇒ page 203

♦ The high pressure and low pressure

equate to the specification

Possible deviation from specification during pressure tes

♦ The required cooling outpuis noreached.

♦ High pressure remains constanor increases only slightly (above the pressure measured when the engine

is stationary).

♦ The low pressure does nodrop or only marginally

Possible causes for deviation from specification and rectification

♦ Actuation of the air conditioner compressor regulating valve - N280- is defective.

– Check actuation of the air conditioner compressor regulating valve - N280- and repair if necessary ⇒ Vehicle

diagnostic tester in “Guided FaulFinding” mode - air conditioning system.

♦ Air conditioner compressor regulating valve - N280- or air conditioner compressor defective

– Check function of -N280- ; if necessary remove -N280- and check for dir⇒ Vehicle diagnostic tester in

“Guided FaulFinding” mode - air conditioning system and ⇒ page 79

– -N280- or renew the air conditioner compressor ⇒ page 79

– If diris found in the refrigerancircuit, clean the refrigerancircui(flush with R1234yf refrigerant) and renew

the expansion valve and desiccanbag/desiccancartridge (or renew the receiver/reservoir) ⇒ page 79 and

⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerancircui(vehicle-specific workshop manual) as well as

⇒ “1.6 Cleaning refrigerancircuit”, page 92 .

Final measures

– Recharge the refrigerancircui⇒ “2.6 Charging refrigerancircuit”, page 146

– Repeat the tes

⇒ “2.14.4 Checking pressures with air conditioning system switched on - vehicles with mechanical air

conditioning compressor”, page 183

192

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Note

♦ If this problem is encountered, ensure thathe air conditioner

compressor (air conditioner compressor shaft) is actually be‐

ing driven via the pulley/drive uni⇒ Heating, air conditioning;

Rep. gr. 87 ; Refrigerancircui(vehicle-specific workshop

manual) and ⇒ Heating, air conditioning; Rep. gr. 87 ; Re‐

frigerancircui(vehicle-specific workshop manual).

♦ If no faulcan be found for this complaint, clean the refrigeran

circui(flush with R1234yf refrigerant)

⇒ “1.6 Cleaning refrigerancircuit”, page 92 .

♦ Check the measured values of the evaporator outputemper‐

ature sender - G263- and actuation of -N280- . If the measured

value of -G263- is faulty, the evaporator could ice up or the

cooling outpumay nobe reached ⇒ Vehicle diagnostic tester

in “Guided FaulFinding” mode - air conditioning system.

♦ If, after repeating the teswhen the expansion valve has been

renewed, the air conditioning system is nooperating correctly,

clean the refrigerancircui(flush with R1234yf refrigerant)

⇒ “1.6 Cleaning refrigerancircuit”, page 92 . Then renew the

air conditioner compressor and desiccaninsert/desiccancar‐

tridge (or reservoir/receiver) ⇒ Heating, air conditioning; Rep.

gr. 87 ; Refrigerancircui(vehicle-specific workshop manual).

♦ In this case, the evaporator may ice up even though the correc

volume of refrigeranis presenin the refrigerancircuit.

♦ If the expansion valve is defective (always closed or noopen‐

ing wide enough), -N280- will change to maximum power and

the low pressure will fall to the diagram value or less (the air

conditioner compressor is drawing the refrigeranouof the

low pressure side) ⇒ Vehicle diagnostic tester in “Guided Faul

Finding” mode - air conditioning system. However, since no

refrigerancan flow through the expansion valve, the required

cooling outpuis noreached, the high pressure may also no

rise or only marginally since no energy exchange is taking

place.

lk

Possible deviation from specification during pressure tes

♦ The required cooling outpuis noreached.

♦ The high pressure equates to the specification

♦ The low pressure equates to the specification or is too low

Possible causes for deviation from specification and rectification

♦ There is too little refrigeranin the refrigerancircuit.

♦ The expansion valve is defective.

– Extract refrigeranfrom the refrigerancircui⇒ “2.4 Emptying refrigerancircuit”, page 137 .

– If the extracted refrigeranvolume is considerably less than the specified fill volume (more than 100 g less)

⇒ Heating, air conditioning; Rep. gr. 00 ; Technical data (vehicle-specific workshop manual), search for

the leak and rectify the cause ⇒ “1.4 Investigating leaks”, page 68

– The extracted refrigeranvolume approximately equates to the prescribed fill volume, renew the expansion

valve for the evaporator in the heater and air conditioning uni⇒ Heating, air conditioning; Rep. gr. 87 ;

Refrigerancircui(vehicle-specific workshop manual)

Final measures

2. Working with air conditioner service station

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lk

Possible deviation from specification during pressure tes

– Recharge the refrigerancircui⇒ “2.6 Charging refrigerancircuit”, page 146

– Repeat the tes

⇒ “2.14.4 Checking pressures with air conditioning system switched on - vehicles with mechanical air

conditioning compressor”, page 183

Note

♦ Check the measured values of the evaporator outputemper‐

ature sender - G263- and actuation of -N280- . If the measured

value of -G263- is faulty, the evaporator could ice up or the

cooling outpumay nobe reached ⇒ Vehicle diagnostic tester

in “Guided FaulFinding” mode - air conditioning system.

♦ If, after repeating the teswhen the expansion valve has been

renewed, the air conditioning system is nooperating correctly,

clean the refrigerancircui(flush with R1234yf refrigerant)

⇒ “1.6 Cleaning refrigerancircuit”, page 92 . Then renew the

air conditioner compressor and reservoir/receiver (or desic‐

cancartridge) ⇒ Heating, air conditioning; Rep. gr. 87 ;

Refrigerancircui(vehicle-specific workshop manual).

Possible deviation from specification during pressure tes

♦ The requisite cooling outpuis noreached.

♦ High pressure does noincrease or only marginally above the pressure with the engine stationary

♦ The low pressure does nodrop or only marginally

Possible causes for deviation from specification and rectification

♦ The air conditioner compressor is nodriven or nodriven athe specified speed

– Check the drive of the air conditioner compressor (via belts or drive unit) ⇒ Heating, air conditioning; Rep.

gr. 87 ; Air conditioner compressor (vehicle-specific workshop manual).

♦ Actuation of the air conditioner compressor regulating valve - N280- (the air conditioning system magnetic

clutch - N25- ) is defective.

– Check actuation of the air conditioner compressor regulating valve - N280- (and the air conditioning system

magnetic clutch - N25- ) and repair if necessary ⇒ Vehicle diagnostic tester in “Guided FaulFinding” mode

- air conditioning system.

♦ Air conditioner compressor regulating valve - N280- or air conditioner compressor defective

– Check function of -N280- ; if necessary remove -N280- and check for dir⇒ Vehicle diagnostic tester in

“Guided FaulFinding” mode - air conditioning system and ⇒ page 79

– -N280- or renew the air conditioner compressor ⇒ page 79

– If diris found in the refrigerancircuit, clean the refrigerancircui(flush with R1234yf refrigerant) and renew

the expansion valve and desiccanbag/desiccancartridge (or renew the receiver/reservoir) ⇒ page 79 ,

⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerancircui(vehicle-specific workshop manual) and

⇒ “1.6 Cleaning refrigerancircuit”, page 92 .

♦ Bottle-neck or blockage in refrigerancircui(e.g. in refrigeranline between service connection on “low

pressure side” and air conditioner compressor).

– Touch the refrigerancircuiby hand to feel for a drop in temperature ⇒ Heating, air conditioning; Rep. gr.

87 ; Refrigerancircui(vehicle-specific workshop manual). If a drop in temperature is felon a component,

if there is a kink or bottle-neck in the hose or pipeline, renew this component. In the evenof a blockage or

if no faulcan be found, clean the refrigerancircui(flush with R1234yf refrigerant)

⇒ “1.6 Cleaning refrigerancircuit”, page 92

– Renew the expansion valve and desiccanbag/desiccancartridge (or reservoir/receiver) ⇒ page 79 and

⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerancircui(vehicle-specific workshop manual).

Final measures

194

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Air conditioning systems with refrigeranR1234yf - General information - Edition 07.2017

Possible deviation from specification during pressure tes

– Recharge the refrigerancircui⇒ “2.6 Charging refrigerancircuit”, page 146

– Repeat the tes

⇒ “2.14.4 Checking pressures with air conditioning system switched on - vehicles with mechanical air

conditioning compressor”, page 183

Note

♦ If this problem is encountered, ensure thathe air conditioner

compressor (air conditioner compressor shaft) is actually be‐

ing driven via the pulley / drive uni(take note of overload

safety device) ⇒ Heating, air conditioning; Rep. gr. 87 ; Re‐

frigerancircui(vehicle-specific workshop manual).

♦ On certain engines, air conditioner compressors are used tha

feature in addition to -N280- an air conditioning system mag‐

netic clutch - N25- on the belpulley. In the evenof this

problem, make sure tha-N25- is actually being actuated and

thathe air conditioner compressor (air conditioner compres‐

sor shaft) is being driven by the pulley ⇒ Heating, air condi‐

tioning; Rep. gr. 87 ; Refrigerancircui(vehicle-specific

workshop manual) and ⇒ Electronic parts catalogue .

♦ If no faulcan be found for this complaint, clean the refrigeran

circui(flush with R1234yf refrigerant)

⇒ “1.6 Cleaning refrigerancircuit”, page 92 .

lk

♦ Check the measured values of the evaporator outputemper‐

ature sender - G263- and actuation of -N280- . If the measured

value of -G263- is faulty, the evaporator could ice up or the

cooling outpumay nobe reached ⇒ Vehicle diagnostic tester

in “Guided FaulFinding” mode - air conditioning system.

♦ If, after repeating the teswhen the expansion valve has been

renewed, the air conditioning system is nooperating correctly,

clean the refrigerancircui(flush with R1234yf refrigerant)

⇒ “1.6 Cleaning refrigerancircuit”, page 92 . Then renew the

air conditioner compressor and reservoir/receiver (or desic‐

cancartridge) ⇒ Heating, air conditioning; Rep. gr. 87 ;

Refrigerancircui(vehicle-specific workshop manual).

♦ If the expansion valve is defective (always closed or noopen‐

ing wide enough), -N280- will change to maximum power and

the low pressure will fall to the diagram value or less (the air

conditioner compressor is drawing the refrigeranouof the

low pressure side) ⇒ Vehicle diagnostic tester in “Guided Faul

Finding” mode - air conditioning system. However, since no

refrigerancan flow through the expansion valve, the required

cooling outpuis noreached, the high pressure may also no

rise or only marginally since no energy exchange is taking

place.

Possible deviation from specification during pressure tes

♦ The requisite cooling outpuis noreached.

♦ The high pressure increases beyond the specified value

♦ Low pressure drops quickly to the specification or lower.

Possible causes for deviation from specification and rectification

2. Working with air conditioner service station

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Air conditioning systems with refrigeranR1234yf - General information - Edition 07.2017

Possible deviation from specification during pressure tes

♦ Actuation of the air conditioner compressor regulating valve - N280- is defective.

– Check the actuation of -N280- and, if necessary, repair ⇒ Vehicle diagnostic tester in “Guided FaulFinding”

mode - air conditioning system.

♦ Constriction or obstruction in refrigerancircui

♦ Expansion valve defective

♦ If a shut-off valve is installed in the refrigerancircuiand idoes noopen correctly or aall ⇒ Heating, air

conditioning; Rep. gr. 87 ; Refrigerancircui(vehicle-specific workshop manual).

– If fitted, check the function of the installed shut-off valve ⇒ Heating, air conditioning; Rep. gr. 87 ; Refrig‐

erancircui(vehicle-specific workshop manual).

– Touch the refrigerancircuiby hand to feel for a drop in temperature ⇒ Heating, air conditioning; Rep. gr.

87 ; Refrigerancircui(vehicle-specific workshop manual). If a drop in temperature is felon a component,

if there is a kink or bottle-neck in the hose or pipeline, renew this component. In the evenof a blockage or

if no faulcan be found, clean the refrigerancircui(flush with R1234yf refrigerant)

⇒ “1.6 Cleaning refrigerancircuit”, page 92

– Renew the expansion valve and desiccanbag/desiccancartridge (or reservoir/receiver) ⇒ page 79 and

⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerancircui(vehicle-specific workshop manual).

Final measures

lk

– Recharge the refrigerancircui⇒ “2.6 Charging refrigerancircuit”, page 146

– Repeat the tes

⇒ “2.14.4 Checking pressures with air conditioning system switched on - vehicles with mechanical air

conditioning compressor”, page 183

Note

♦ In this case, the evaporator may ice up even though the correc

volume of refrigeranis presenin the refrigerancircuit.

♦ If the expansion valve is defective (always closed or noopen‐

ing wide enough) the air conditioner compressor regulating

valve - N280- will be seto maximum power and the low pres‐

sure value will fall to the diagram value or less (the air condi‐

tioner compressor extracts refrigeranfrom the low pressure

side). Since no refrigerancan flow through the expansion

valve, however, the cooling outpuis noreached and the high

pressure may also noincrease or only increase slightly owing

to there being no energy exchange ⇒ Vehicle diagnostic tester

in “Guided FaulFinding” mode - air conditioning system and

⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerancircui

(vehicle-specific workshop manual).

♦ If there is too much refrigeranin the refrigerancircuit, the air

conditioner compressor musbe emptied and the desiccan

bag (desiccancartridge) or reservoir/receiver renewed. After

cleaning (flushing with R1234yf refrigerant)

⇒ “1.6 Cleaning refrigerancircuit”, page 92 the refrigerancir‐

cuit, pour the correcvolume of refrigeranoil in the refrigeran

circui⇒ Heating, air conditioning; Rep. gr. 00 ; Technical

data; Approved refrigeranoils and refrigeranoil fill volumes

(vehicle-specific workshop manual) and ⇒ Heating, air con‐

ditioning; Rep. gr. 87 ; Refrigerancircui(vehicle-specific

workshop manual).

♦ If the specification is noreached again when the tesis re‐

peated buno faulcan be found in the refrigerancircuit, clean

the refrigerancircui(flush with R1234yf refrigerant)

⇒ “1.6 Cleaning refrigerancircuit”, page 92 .

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Air conditioning systems with refrigeranR1234yf - General information - Edition 07.2017

Possible deviation from specification during pressure tes

♦ The requisite cooling outpuis reached initially buafter a while or after an extended period, the cooling

outpuis no longer sufficient.

♦ The high pressure and the low pressure are normal to starwith

♦ After some time, the high pressure rises above the specification, the low pressure still equates to the

specification or idrops below the specification.

Possible causes for deviation from specification and rectification

♦ Radiator, condenser contaminated or actuation of the radiator is noOK

– Check actuation of the radiator fan and repair if necessary ⇒ Vehicle diagnostic tester in “Guided Faul

Finding” mode - air conditioning system.

– Check condenser for contamination and clean if necessary ⇒ Heating, air conditioning; Rep. gr. 87 ;

Refrigerancircui(vehicle-specific workshop manual) and ⇒ Engine, mechanicals; Rep. gr. 19 ; Radiator/

radiator fan .

♦ Actuation of the air conditioner compressor regulating valve - N280- is defective.

– Check actuation of -N280- and the measured value of evaporator outputemperature sender - G263- ,

repair if necessary ⇒ Vehicle diagnostic tester in “Guided FaulFinding” mode - air conditioning system.

♦ Too much refrigeranin the refrigerancircui

– Extract refrigeranfrom the refrigerancircui⇒ “2.4 Emptying refrigerancircuit”, page 137 .

– If the extracted refrigeranvolume is considerably greater (more than 100 g) than the prescribed fill volume

⇒ Heating, air conditioning; Rep. gr. 00 ; Technical data (vehicle-specific workshop manual), there was

too much refrigeranin the refrigerancircuiRefill the refrigerancircuiwith the correcvolume of R1234yf

and repeathe test.

♦ Air conditioner compressor regulating valve - N280- or air conditioner compressor defective

– Check function of -N280- ; if necessary remove -N280- and check for dir⇒ Vehicle diagnostic tester in

“Guided FaulFinding” mode - air conditioning system and ⇒ “1.5 Renewing components”, page 79

– -N280- or renew the air conditioner compressor ⇒ “1.5 Renewing components”, page 79

– If diris found in the refrigerancircuit, clean the refrigerancircui(flush with R1234yf refrigerant) and renew

the expansion valve and desiccanbag/desiccancartridge (or renew the receiver/reservoir)

⇒ “1.5 Renewing components”, page 79 and ⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerancircui

lk

(vehicle-specific workshop manual) and ⇒ “1.6 Cleaning refrigerancircuit”, page 92 .

♦ Too much refrigeranoil in the refrigerancircui

♦ Moisture in refrigerancircui

– Extract refrigeranfrom the refrigerancircui⇒ “2.4 Emptying refrigerancircuit”, page 137 .

– If the extracted refrigeranvolume equates to the prescribed fill volume or is marginally lower (max. 100 g)

⇒ Heating, air conditioning; Rep. gr. 00 ; Technical data (vehicle-specific workshop manual), there is too

much refrigeranoil in the refrigerancircui

– Clean refrigerancircui(flush with R1234yf refrigerant) ⇒ “1.6 Cleaning refrigerancircuit”, page 92 .

– Renew the expansion valve and desiccanbag/desiccancartridge (or reservoir/receiver)

⇒ “1.5 Renewing components”, page 79 and ⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerancircui

(vehicle-specific workshop manual).

Final measures

– Recharge the refrigerancircui⇒ “2.6 Charging refrigerancircuit”, page 146

– Repeat the tes

⇒ “2.14.4 Checking pressures with air conditioning system switched on - vehicles with mechanical air

conditioning compressor”, page 183

2. Working with air conditioner service station

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Air conditioning systems with refrigeranR1234yf - General information - Edition 07.2017

Note

♦ If there is too much refrigeranin the refrigerancircuit, the air

conditioner compressor musbe emptied and the desiccan

bag (desiccancartridge) or reservoir/receiver renewed. After

cleaning (flushing with R1234yf refrigerant)

⇒ “1.6 Cleaning refrigerancircuit”, page 92 the refrigerancir‐

cuit, pour the correcvolume of refrigeranoil in the refrigeran

circui⇒ Heating, air conditioning; Rep. gr. 00 ; Technical

data; Approved refrigeranoils and refrigeranoil fill volumes

(vehicle-specific workshop manual) and ⇒ Heating, air con‐

ditioning; Rep. gr. 87 ; Refrigerancircui(vehicle-specific

workshop manual).

♦ In this case, the evaporator may ice up even though the correc

volume of refrigeranis presenin the refrigerancircuit.

♦ A faulin the evaporator outputemperature sender - G263-

could also cause the refrigerancircuito ice up. With this

complaint, also observe the measured value of -G263- ⇒ Ve‐

hicle diagnostic tester in “Guided FaulFinding” mode - air

conditioning system and ⇒ Heating, air conditioning; Rep. gr.

87 ; Overview of fitting locations - air conditioning system (ve‐

hicle-specific workshop manual).

lk

Possible deviation from specification during pressure tes

♦ The requisite cooling outpuis reached initially buafter a shoror extended period, the required level is no

longer reached.

♦ The high pressure and low pressure are normal to starwith buafter a while, the high pressure rises above

the specification and the low pressure drops to the specification or lower.

♦ The high pressure and low pressure are normal to starwith. After a while, the low pressure drops to the

specification or lower and the evaporator ices up.

Possible causes for deviation from specification and rectification

198

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Air conditioning systems with refrigeranR1234yf - General information - Edition 07.2017

Possible deviation from specification during pressure tes

♦ Radiator, condenser contaminated or actuation of the radiator is noOK

– Check actuation of the radiator fan and repair if necessary ⇒ Vehicle diagnostic tester in “Guided Faul

Finding” mode - air conditioning system.

– Check condenser for contamination and clean if necessary ⇒ Heating, air conditioning; Rep. gr. 87 ;

lk

Refrigerancircui(vehicle-specific workshop manual) and ⇒ Engine, mechanicals; Rep. gr. 19 ; Radiator/

radiator fan .

♦ Measured value of evaporator outputemperature sender - G263- faulty.

– Check measured value and installation of -G263- ⇒ Vehicle diagnostic tester in “Guided FaulFinding”

function - air conditioning system and ⇒ Heating, air conditioning; Rep. gr. 87 ; Overview of fitting locations

- air conditioning system .