Get Air conditioning system -> 1.2 General description - components of refrigerant circuit Guide for Volkswagen Touran 4 Door Second Generation (2015-2022)

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Air conditioning systems with refrigerant R1234yf - General information - Edition 07.2017

1.2

General description - components of re‐

frigerant circuit

⇒ “1.2.1 Layout and function of refrigerant circuit”, page 36

⇒ “1.2.2 Mechanical air conditioner compressor”, page 38

⇒ “1.2.3 Electrical air conditioner compressor for hybrid vehicles”,

page 40

⇒ “1.2.4 Condenser”, page 43

⇒ “1.2.5 Evaporator”, page 43

⇒ “1.2.6 Reservoir”, page 44

⇒ “1.2.7 Heat exchanger for heat pump mode”, page 45

⇒ “1.2.8 Liquid receiver”, page 45

⇒ “1.2.9 Restrictor”, page 46

⇒ “1.2.10 Receiver”, page 47

⇒ “1.2.11 Expansion valve (with and without shut-off valve)”, page

48

⇒ “1.2.12 Refrigerant shut-off valves”, page 50

⇒ “1.2.13 Refrigerant line with internal heat exchanger”,

page 51

⇒ “1.2.14 Quick release couplings of refrigerant lines”,

page 51

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⇒ “1.2.15 Seals”, page 52

⇒ “1.2.16 Pipes and hoses in refrigerant circuit”, page 52

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

⇒ “1.2.18 Non-return valves”, page 54

⇒ “1.2.19 Quick-release coupling connections in refrigerant cir‐

cuit”, page 55

⇒ “1.2.20 Connections with valve for switches in refrigerant circuit

”, page 59

⇒ “1.2.21 Pressure senders and switches in refrigerant circuit”,

page 59

⇒ “1.2.22 Refrigerant pressure and temperature sender”,

page 60

⇒ “1.2.23 Air conditioner compressor regulating valve N280 ”,

page 63

⇒ “1.2.24 Refrigerant temperature sender”, page 63

1.2.1

Layout and function of refrigerant circuit

♦ Located on the high-pressure side are the condenser, receiver

and restrictor or expansion valve to separate the high-pres‐

sure side (HD) and low-pressure side (ND).

♦ High pressure is created by the restrictor or expansion valve

forming a constriction and causing the refrigerant to build up,

thus leading to increased pressure and temperature.

♦ Excessive pressure results if the circuit is filled with too much

refrigerant or refrigerant oil, or the condenser is dirty, the ra‐

diator fan is defective, there is a blockage in the system or

there is moisture in the refrigerant circuit (causing the restrictor

or expansion valve to ice up).

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Rep. gr.87 - Air conditioning system

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♦ Located on the low-pressure side are the evaporator, the tem‐

perature sensor for the evaporator and the air conditioner

compressor that acts as the separation between the high-

pressure (HD) and low-pressure (ND) gas sides.

♦ A loss of pressure in the system can be due to loss of refrig‐

erant, restrictor or expansion valve defective or blocked, de‐

fective air conditioner compressor or an iced-up evaporator.

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1. Refrigerant circuit

37

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1.2.2

Mechanical air conditioner compressor

The air conditioner compressor is driven by a poly V-belt -B- or a

shaft by the engine.

Air conditioner compressor with air conditioning system magnetic

clutch - N25- :

An electromagnetic clutch -A- attached to the air conditioner com‐

pressor provides power transfer between pulley -B- and com‐

pressor crankshaft when the air conditioning is switched on.

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An overload protection device attached to the clutch plate or fitted

in the solenoid of the air conditioner compressor triggers if there

is resistance in the air conditioner compressor (sluggish move‐

ment), protecting the belt drive or the drive unit against overload.

Note

♦ To ensure that the air conditioner compressor is not damaged

if the refrigerant circuit is empty, the air conditioner compres‐

sor regulating valve - N280- and, under certain circumstances,

the air conditioning system magnetic clutch - N25- are no lon‐

ger actuated (the air conditioner compressor only runs at idle

with the engine if -N25- is actuated).

♦ An air conditioner compressor with -N25- (without -N280- ) is

not actuated if the refrigerant circuit is empty and is therefore

not driven.

Air conditioner compressor without air conditioning system mag‐

netic clutch - N25- :

♦ An overload protection device attached to the pulley -B- or fit‐

ted in the drive unit of the air conditioner compressor triggers

if there is resistance in the air conditioner compressor (slug‐

gish movement), protecting the belt drive or the drive unit

against overload.

♦ An air conditioner compressor with air conditioner compressor

regulating valve - N280- (without -N25- ) is switched over to

internal lubrication via a valve if the refrigerant circuit is empty.

Note

♦ On air conditioner compressors without air conditioning sys‐

tem magnetic clutch - N25- , the engine may only be started

following complete assembly of the refrigerant circuit.

♦ To ensure that the air conditioner compressor suffers no dam‐

age if the refrigerant circuit is empty, the air conditioner com‐

pressor regulating valve - N280- is no longer activated (the air

conditioner compressor idles with the engine).

All air conditioner compressors

The air conditioner compressor draws refrigerant gas from the

evaporator, compresses it and sends it to the condenser.

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Rep. gr.87 - Air conditioning system

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Air conditioning systems with refrigerant R1234yf - General information - Edition 07.2017

Note

♦ The air conditioner compressor contains refrigerant oil, which

can be mixed with R1234yf refrigerant at any temperature.

♦ The identification plate states the refrigerant for which the air

conditioner compressor is suitable. A valve regulates the pres‐

sure on the low-pressure side within the specified range (con‐

trol characteristic) ⇒ Heating, air conditioning system; Rep.

gr. 87 ; Refrigerant circuit .

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♦ Depending on the version of air conditioner compressor, dif‐

ferent refrigerant oils are filled in the air conditioner compres‐

sor. Refrigerant oils that were developed for R134a refrigerant

oil only, must not be used for R1234yf refrigerant ⇒ Heating,

air conditioning system; Rep. gr. 00 ; Technical data; Refrig‐

erant oil .

♦ Air conditioner compressors with or without air conditioning

system magnetic clutch - N25- are currently actuated via an

air conditioner compressor regulating valve - N280- -C- exter‐

nally ⇒ Heating, air conditioning system; Rep. gr. 87 ; Re‐

frigerant circuit .

♦ The identification plate states the refrigerant for which the air

conditioner compressor is suitable. An air conditioner com‐

pressor regulating valve - N280- regulates the pressure on the

low-pressure side within the specified range (control charac‐

teristic) ⇒ Heating, air conditioning system; Rep. gr. 87 ;

Refrigerant circuit .

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

tuated externally ⇒ Vehicle diagnostic tester in “Guided Fault

Finding” in air conditioning system.

♦ The engine must not be started in a vehicle with air conditioner

compressor but no air conditioner compressor magnetic clutch

- N25- if there is negative pressure in the refrigerant circuit

(e.g. during evacuation) ⇒ page 129 .

♦ The engine may only be started in a vehicle with air conditioner

compressor but no air conditioner compressor magnetic clutch

- N25- when the refrigerant circuit has been completely as‐

sembled.

♦ To ensure that the air conditioner compressor suffers no dam‐

age if the refrigerant circuit is empty, the air conditioner com‐

pressor regulating valve - N280- is no longer activated (the air

conditioner compressor idles with the engine) if the pressure

in the refrigerant circuit is too low (lower than approx. 2 bar).

♦ An air conditioner compressor with air conditioner compressor

regulating valve - N280- is switched over to internal lubrication

via a valve if the refrigerant circuit is empty.

♦ Depending on the version of air conditioner compressor, a

valve may be installed on the high-pressure side that prevents

liquefied refrigerant flowing 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 refrigerant circuit with expansion valve, it could

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 refrigerant only 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 refrigerant can flow on the low-pressure

side.

1. Refrigerant circuit

39

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♦ On an air conditioner compressor with electromagnetic clutch

-A- and regulating valve -C-, the electromagnetic clutch -A- is

usually only actuated if the regulating valve -C- is also actu‐

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

erant circuit .

1.2.3

Electrical air conditioner compressor for

hybrid vehicles

Vehicles with high-voltage system (hybrid vehicles)

If repair work in the vicinity of high-voltage components and ca‐

bles is necessary, inspect high-voltage components and cables

for damage ⇒ page 4 ⇒ Electrical system; Rep. gr. 93 ; General

warnings for work on the high-voltage system .

If work on the components of the high-voltage system is neces‐

sary, ensure that the high-voltage system is de-energised ⇒ Rep.

gr. 93 ; De-energising high-voltage system .

De-energise the high-voltage system and restarting the high-volt‐

age system ⇒ Rep. gr. 93 ; De-energising high-voltage system

– To minimise the number of automatic engine starts when the

vehicle's drive system is active (READY) during test and

measurement work, charge the vehicle batteries e.g. with the

battery charger 60 A - VAS 5904- in battery standby mode ⇒

Electrical system - General information; Rep. gr. 27 ; Charging

battery and ⇒ Electrical system; Rep. gr. 93 ; General warn‐

ings for work on the high-voltage system .

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– For testing and measuring work that requires the vehicle's

drive system to be active (READY) or the ignition to be switch‐

ed on, move the selector lever to position “P”, activate the

parking brake, and arrange the tools needed so that they can‐

not come into contact with moving components of the engine

and so that they cannot even come near to components that

turn when the engine is running.

Electrical air conditioner compressor

NOTICE

Risk of irreparable damage to electrical air conditioner com‐

pressor from short circuit.

– Never touch the air conditioner compressor when switching

on the ignition or starting the drive machines.

♦ The air conditioner compressor draws refrigerant gas from the

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evaporator, compresses it and sends it to the condenser.

♦ The electric motor of the air conditioner compressor is sup‐

plied with power e.g. from the power and control electronics

for electric drive - JX1- ⇒ Current flow diagrams, Electrical fault

finding and Fitting locations.

♦ The control unit for air conditioner compressor - J842- inte‐

grated in the air conditioner compressor regulates the speed

and thereby the performance of the air conditioner compressor

( electrical air conditioner compressor - V470- ) according to

the request received via the data bus ⇒ Vehicle diagnostic

tester in “Guided Fault Finding” function of air conditioning

system and battery control system

♦ There is no air conditioner compressor regulating valve -

N280- in the electrical air conditioner compressor.

♦ The bolting points of the air conditioner compressor and the

bracket must be checked prior to installation. The contact sur‐

faces must be free of dirt, rust and grease. Otherwise, repair

contact surfaces using contact surface cleaning set - VAS

6410- ⇒ Electrical system; General information; Rep. gr. 97 ;

Wiring harness and connector repair .

1. Refrigerant circuit

41

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Note

♦ If the air conditioner compressor control unit - J842- is defec‐

tive, the amount of refrigerant oil in the new air conditioner

compressor must be adjusted. The refrigerant circuit must not

be cleaned (flushed) with R1234yf.

♦ The control unit for air conditioner compressor - J842- and the

electrical air conditioner compressor - V470- are one compo‐

nent and can currently not be separated.

♦ There is no -N280- installed in the electrical air conditioner

compressor. The power of the air conditioner compressor is

regulated externally by the speed of the air conditioner com‐

pressor ⇒ Current flow diagrams, Electrical fault finding and

Fitting locations and ⇒ Vehicle diagnostic tester in “Guided

Fault Finding” mode - air conditioning system and battery reg‐

ulation.

♦ The electrical air conditioner compressor currently works in

the same way as a spiral or scroll-type charger (similar to a G-

Lader).

♦ The air conditioner compressor contains refrigerant oil, which

can be mixed with R1234yf refrigerant at any temperature.

♦ The identification plate states the refrigerant for which the air

conditioner compressor is suitable.

♦ The integrated electronics regulate the performance of the air

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conditioner compressor via the speed (and thereby the pres‐

sure on the low-pressure side) within the specific target range

(control characteristic).

♦ The engine should be started only when the refrigerant circuit

has been fully assembled.

♦ The air conditioner compressor has an internal oil circuit to

ensure that the air conditioner compressor is not damaged

when the refrigerant circuit is empty. This means that approx.

40 to 50 cm³of refrigerant oil remain in the air conditioner

compressor.

♦ Just like the mechanical air conditioner compressor, the elec‐

trical air conditioner compressor has a pressure relief valve.

♦ On vehicles with battery cooling, electric and hybrid operation

is only possible with the air conditioning system charged and

no faults stored in connection with the air conditioning system

⇒ Vehicle diagnostic tester in “Guided Fault Finding” mode -

air conditioning system and battery regulation.

♦ First bring the electrical air conditioner compressor into oper‐

ation after installing the air conditioner compressor and charg‐

ing the refrigerant circuit via the “Compressor run-in” function

in basic settings. Should there be an accumulation of refriger‐

ant oil in the compression chamber of the air conditioner

compressor before installation owing to unfavourable storage,

damage could be caused to the air conditioner compressor

⇒ Vehicle diagnostic tester in “Guided Fault Finding” mode -

air conditioning system and battery regulation.

♦ An electrically driven air conditioner compressor may only be

activated when the refrigerant circuit is charged. Running the

air conditioner compressor with the refrigerant circuit empty

could lead to compressor damage ⇒ Vehicle diagnostic tester

in “Guided Fault Finding” mode.

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Rep. gr.87 - Air conditioning system

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1.2.4

Condenser

♦ The condenser -A- transfers heat from the compressed refrig‐

erant gas into the surrounding air.

♦ When this happens, the refrigerant gas condenses to liquid.

Note

♦ Depending on the design of the refrigerant circuit, the receiver

may be attached to the condenser or integrated in the con‐

denser ⇒ Heating, air conditioning system; Rep. gr. 87 ;

Refrigerant circuit (vehicle-specific workshop manual) and ⇒

Electronic parts catalogue .

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♦ There are different versions of the condenser; from the outside

these versions can only be identified by their part number.

Version -1- of the condenser is split into two sections (“two-

pass condenser”). Version -2- of the condenser is split into four

sections (“four-pass condenser”).

♦ This illustration shows a condenser with the receiver -C- at‐

tached.

♦ The gaseous refrigerant enters the condenser at connection

-A-; the refrigerant is then cooled down in the condenser and

turns into liquid.

♦ The liquid refrigerant accumulates in receiver -C- (with dryer)

and flows through the bottom cooling section to connection

-B-.

♦ The refrigerant capacity in a refrigerant circuit may differ de‐

pending on the design of the condenser (internal volume, flow,

etc.). Therefore, always ensure the version and allocation of

the condenser are correct ⇒ Heating, air conditioning system;

Rep. gr. 00 ; Technical data (vehicle-specific workshop man‐

ual) and ⇒ Electronic parts catalogue .

1.2.5

Evaporator

There are different types of evaporator. Depending on the design

and function, the thermal energy that is needed to evaporate the

refrigerant is drawn from the air flowing through the system (e.g.

with the evaporator in heater and air conditioning unit or in the

battery cooling module) or the coolant flowing through the system

(e.g. with the heat exchanger for the high-voltage battery) ⇒

Heating, air conditioning system; Rep. gr. 87 ; Refrigerant circuit;

System overview - refrigerant circuit (vehicle-specific workshop

manual).

Note

The following describes 2 versions of the evaporator.

1. Refrigerant circuit

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Evaporator in heating and air conditioning system (or in the bat‐

tery cooling module)

♦ The liquid refrigerant evaporates in the pipelines of the evap‐

orator -A-. The heat required to do this is drawn from the air

flowing over the evaporator fins -B-. The air cools down. The

refrigerant evaporates and is drawn into the air conditioning

system compressor carrying with it the heat it has absorbed.

♦ A defined quantity of refrigerant is fed to the evaporator

through an expansion valve (restrictor). In systems with an

expansion valve the flow rate is regulated such that only gas‐

eous refrigerant emerges at the evaporator outlet.

♦ When R1234yf refrigerant was introduced, the evaporators

were adapted to the refrigerant, hence the need to observe the

correct version ⇒ Electronic parts catalogue .

Evaporator / heat exchanger for high-voltage battery (chiller)

The liquid refrigerant evaporates in the evaporator (heat ex‐

changer). The heat required to do this is drawn from the coolant

that flows through the evaporator. The coolant cools. The refrig‐

erant evaporates and is drawn into the air conditioner compressor

carrying with it the heat it has absorbed.

A defined quantity of refrigerant is fed to the evaporator through

a restrictor (or an expansion valve) and a shut-off valve. The flow

rate of the coolant (or refrigerant) is regulated in such a way that

only gaseous refrigerant escapes at the evaporator outlet ⇒

Heating, air conditioning; Rep. gr. 87 ; Refrigerant circuit; System

overview - refrigerant circuit (vehicle-specific workshop manual).

1.2.6

Reservoir

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Note

This type of air conditioning system is currently only installed in

systems with a restrictor.

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♦ The reservoir collects the vaporised and gaseous mixture

coming from the evaporator to ensure the air conditioner com‐

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pressor receives only gaseous refrigerant. The vapour be‐

comes gaseous refrigerant.

♦ Refrigerant oil flowing in the circuit does not remain in the res‐

ervoir because an oil extraction hole has been provided.

♦ Any moisture ingress into the refrigerant circuit during assem‐

bly is trapped by a filter (desiccant bag) in the reservoir.

♦ Gaseous refrigerant with oil is drawn in by the air conditioner

compressor.

Note

♦ Renew the reservoir if the refrigerant circuit has been open for

an extended period of time and moisture has entered or if re‐

quired to do so owing to a specific complaint ⇒ page 79 .

♦ Do not remove sealing plugs -A- and -B- until just before in‐

stallation.

♦ A dryer kept in an unsealed reservoir is saturated with mois‐

ture after a short time and cannot be used.

♦ When installing, observe arrow indicating direction of flow if

applicable.

1.2.7

Heat exchanger for heat pump mode

The gaseous or vaporous refrigerant compressed by the air con‐

ditioning compressor is liquefied in the heat exchanger -A-. The

heat that is given off in the process is picked-up by the coolant

flowing through the system ⇒ Heating, air conditioning; Rep. gr.

87 ; Refrigerant circuit; System overview - refrigerant circuit .

1.2.8

Liquid receiver

In certain operating conditions (e.g. in heat pump mode), the re‐

ceiver (e.g. on the condenser) is not integrated in the refrigerant

circuit. The receiver -B- collects the refrigerant, temporarily stores

any excess should a certain amount of refrigerant not be required

and then feeds it in a steady flow to the expansion valve (in front

of the evaporator in the heater and air conditioning unit) or to the

heat exchanger in the coolant circuit of the high voltage system

⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerant circuit; Sys‐

tem overview - refrigerant circuit .

1. Refrigerant circuit

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1.2.9

Restrictor

Restrictor in front of evaporator

Note

Currently, there is no air conditioning system with a restrictor in‐

stalled in front of the evaporator.

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♦ The restrictor creates a constriction. This restriction limits the

flow, separating the high pressure and low pressure sides in

the refrigerant circuit. Upstream of the restrictor, the refriger‐

ant is warm due to the high pressure. Downstream of the

restrictor, the refrigerant is cold due to the low pressure. Up‐

stream of the constriction is a strainer to catch dirt and down‐

stream of the constriction is a strainer to atomise the

refrigerant before it enters the evaporator.

Note

♦ Arrow -A- on the restrictor points to the evaporator.

♦ Renew every time the refrigerant circuit is opened.

♦ Note different versions; refer to the various customer service

information ⇒ Electronic parts catalogue .

Restrictor in front of heat exchanger for high-voltage battery (chill‐

er)

The restrictor creates a constriction. This restriction limits the flow,

separating the high pressure and low pressure sides in the re‐

frigerant circuit. Upstream of the restrictor, the refrigerant is warm

due to the high pressure. Downstream of the restrictor, the refrig‐

erant is cold due to the low pressure.

Note

♦ The illustration shows a refrigerant line -A- with a permanently

installed restrictor -B- (without strainer).

♦ The diameter of the shown restrictor hole -B- is

approx. 0.7 mm. Depending on the refrigerant line version, this

restrictor is permanently installed or it can be removed. For the

removable version a strainer may be fitted to prevent the re‐

strictor hole from being blocked by suspended particles.

♦ Check for soiling before installing and clean or renew as nec‐

essary.

♦ Observe different versions.

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Rep. gr.87 - Air conditioning system

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1.2.10

Receiver

♦ The receiver -B- collects the liquid droplets and directs them

in a continuous stream to the expansion valve. Any moisture

that has entered the refrigerant circuit during assembly is col‐

lected by a dryer -D- in the receiver -B-.

♦ Depending on the layout of the refrigerant circuit and the ver‐

sion of condenser -A-, the receiver -B- may be installed on the

condenser -A- or (integrated) in the condenser -A- ⇒ Heating,

air conditioning; Rep. gr. 87 ; Refrigerant circuit (vehicle-spe‐

cific workshop manual) and ⇒ Electronic parts catalogue .

♦ Installed in the receiver -B- is a dryer (e.g. desiccant bag -D-)

and strainer -F- (that filters out smaller contaminants).

Note

♦ The receiver -B- comes in different versions and different de‐

signs ⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerant

circuit (vehicle-specific workshop manual) and ⇒ Electronic

parts catalogue .

♦ Renew the receiver -B- and plastic bolt (with seals) -C-, des‐

iccant cartridge -D-, filter carrier -E- and strainer -F- if the

refrigerant circuit was open for an extended period of time and

moisture has been absorbed, or if required to do so owing to

a specific complaint ⇒ page 79 .

♦ Do not remove the sealing plugs of a receiver until immediately

prior to installation as a desiccant bag in a non-sealed reser‐

voir will become saturated with moisture and become unusa‐

ble.

♦ The desiccant cartridge comes in an air-tight transport bag,

which should remain sealed for as long as possible. Do not

open the transport bag until immediately prior to inserting the

desiccant cartridge -D- in the receiver -B- of the condenser.

After the transport bag has been opened, the desiccant car‐

tridge will become saturated with moisture within a short time

and is then unusable.

♦ When installing, observe arrow indicating direction of flow if

applicable.

♦ The procedure to adopt in the event of a complaint differs de‐

pending on the type of receiver/desiccant cartridge. If the

receiver is installed on the condenser, for example, it can be

renewed completely with the desiccant cartridge. If the receiv‐

er is integrated in the condenser, for example, the desiccant

cartridge and an additional filter element (if one is fitted) can

be replaced individually on most versions. If the receiver is

integrated in the condenser and it is not possible to replace

the receiver/desiccant cartridge separately, it may be neces‐

sary to replace the entire condenser ⇒ Heating, air condition‐

ing; Rep. gr. 87 ; Refrigerant circuit (vehicle-specific workshop

manual) and ⇒ Electronic parts catalogue .

♦ Depending on the layout of the refrigerant circuit (with desic‐

cant bag or desiccant cartridge), the receiver may also be

integrated in the refrigerant circuit (it need not always be in‐

stalled on or in the condenser) ⇒ Heating, air conditioning;

Rep. gr. 87 ; Refrigerant circuit (vehicle-specific workshop

manual) and ⇒ Electronic parts catalogue .

1. Refrigerant circuit

47

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1.2.11

Expansion valve (with and without shut-

off valve)

Expansion valve without shut-off function

The expansion valve -A- atomises incoming refrigerant and reg‐

ulates the flow so that, depending on the heat transport, the

vapour does not become a gas until it reaches the outlet of the

evaporator.

Note

♦ When R1234yf refrigerant was introduced, the expansion

valves were adapted to the refrigerant (different characteris‐

tics), hence the need to observe the correct version ⇒ Elec‐

tronic parts catalogue .

♦ Different versions of expansion valve due to different charac‐

teristics that are matched to the relevant refrigerant circuit ⇒

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

hicle-specific workshop manual) and ⇒ Electronic parts cata‐

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logue .

♦ When renewing the expansion valve, make sure that the part

number is correct ⇒ Electronic parts catalogue .

♦ Depending on the version of air conditioner compressor, a

valve may be installed on the high-pressure side that prevents

liquefied refrigerant flowing 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 refrigerant circuit with expansion valve, it could

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 refrigerant only 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 refrigerant can flow on the low-pressure

side.

Expansion valve with refrigerant shut-off valve

Note

Shut-off valves come in different versions, with different functions

and different designations ⇒ Heating, air conditioning; Rep. gr.

87 ; Refrigerant circuit (vehicle-specific workshop manual).

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Rep. gr.87 - Air conditioning system

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Air conditioning systems with refrigerant R1234yf - General information - Edition 07.2017

♦ The expansion valve -A- with shut-off valve -B- atomises the

incoming refrigerant and regulates the flow rate of the refrig‐

erant to the evaporator in the battery cooling module of the

hybrid battery unit - AX1- in such a way that, depending on the

heat transport, the vapour does not become a gas until it rea‐

ches the outlet of the evaporator.

♦ If the shut-off valve -B- is actuated by the electronics, it is open

and allows refrigerant to flow through to the expansion valve

-A-.

♦ If the shut-off valve -B- is open, the expansion valve -A- allows

refrigerant to flow through to the evaporator or heat exchanger

based on its control characteristic ⇒ Heating, air conditioning;

Rep. gr. 87 ; Refrigerant circuit .

♦ The solenoid -B- attached to the expansion valve -A- is actu‐

ated by different control units depending on the vehicle ⇒ Cur‐

rent flow diagrams, Electrical fault finding and Fitting locations

and ⇒ Vehicle diagnostic tester in “Guided Fault Finding”

mode.

♦ If, on a vehicle with 2 evaporators (one in the heater and air

conditioner unit and one in the battery cooling module, e.g. the

Audi Q5 Hybrid), the temperature measured at one evaporator

meets the specification or falls below the specification, while

on the other evaporator however the requisite specification is

not reached, regulation works as follows: the battery regula‐

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tion control unit - J840- makes the electrical air conditioner

compressor run at a higher speed via the power and control

electronics for electric drive - JX1- and the control unit for air

conditioning compressor - J842- (which results in the cooling

output of the air conditioning system rising and pressure on

the low pressure side falling along with the evaporator tem‐

perature). If, as a result, the temperature at one evaporator

falls below the specified level, -J840- actuates refrigerant shut-

off valve 1 for hybrid battery - N516- or refrigerant shut-off

valve 2 for hybrid battery - N517- in such a way that the evap‐

orator - which is too cold - no longer has refrigerant flowing

through it ⇒ Vehicle diagnostic tester in “Guided Fault Finding”

mode.

1. Refrigerant circuit

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Air conditioning systems with refrigerant R1234yf - General information - Edition 07.2017

1.2.12

Refrigerant shut-off valves

Shut-off valves with 2 switch statuses (open or closed)

♦ Shut-off valves come in different versions, with different func‐

tions and different designations ⇒ Heating, air conditioning;

Rep. gr. 87 ; Refrigerant circuit .

♦ If the shut-off valve -A- is not actuated by the electronics, it is

open and allows refrigerant to flow through.

♦ The shut-off valve -A- is installed on vehicles with high-voltage

system, for example. It is actuated when no climate control is

wanted for the passenger compartment but battery cooling is

required for the hybrid battery unit - AX1- .

♦ Note the arrow -B- on the shut-off valve -A-, which shows the

direction of refrigerant flow (from condenser to evaporator in

the heater and air conditioning unit).

♦ The solenoid -C- attached to the shut-off valve -A- is actuated

by different control units depending on the vehicle ⇒ Current

flow diagrams, Electrical fault finding and Fitting locations and

⇒ Vehicle diagnostic tester in “Guided Fault Finding” mode -

air conditioning system and battery regulation.

♦ If, on a vehicle with 2 evaporators (one in the heater and air

conditioner unit and one in the battery cooling module, e.g. the

Audi Q5 Hybrid), the temperature measured at one evaporator

meets the specification or falls below the specification, while

on the other evaporator however the requisite specification is

not reached, regulation works as follows: the respective con‐

trol unit makes the electrical air conditioner compressor run at

a higher speed (which results in the cooling output of the air

conditioning system rising and pressure on the low pressure

side falling along with the evaporator temperature). If the tem‐

perature at an evaporator then falls below the specified level,

the respective control unit actuates the shut-off valve in such

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a way that the evaporator that is too cold no longer has refrig‐

erant flowing through it ⇒ Heating, air conditioning; Rep. gr.

87 ; Refrigerant circuit and ⇒ Vehicle diagnostic tester in “Gui‐

ded Fault Finding” mode.

Shut-off valves regulated via characteristic curves

♦ The shut-off valve -A- is actuated via an incremental motor

-B- by the respective control unit with characteristic curves

(open or closed).

♦ If the shut-off valve acts as a control valve (e.g. refrigerant

expansion valve 1 - N636- as is the case with the Audi Q7), it

is only opened enough to allow the temperature set for the heat

exchanger to be reached ⇒ Heating, air conditioning; Rep. gr.

87 ; Refrigerant circuit .

♦ Shut-off valves actuated via incremental motors do not have

a defined rest position. For this reason, they have to be set to

a certain position (open or closed) before work on the refrig‐

erant circuit is performed ⇒ Heating, air conditioning; Rep. gr.

87 ; Refrigerant circuit .

♦ Depending on layout of the refrigerant circuit there could be a

cluster of shut-off valves forming a valve block (e.g. on the e-

Golf or Audi Q7 e-tron) ⇒ Heating, air conditioning; Rep. gr.

87 ; Refrigerant circuit .

♦ The incremental motor is programmed and actuated via data

lines (LIN-Bus) by the respective control unit in relation to its

installation location ⇒ Heating, air conditioning; Rep. gr. 87 ;

Refrigerant circuit and ⇒ Vehicle diagnostic tester in “Guided

Fault Finding” mode.

50

Rep. gr.87 - Air conditioning system

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Air conditioning systems with refrigerant R1234yf - General information - Edition 07.2017

1.2.13

Refrigerant line with internal heat ex‐

changer

♦ In this refrigerant line, the warm liquid refrigerant flowing on

the high pressure side supplies energy to the cold refrigerant

gas or vapour flowing on the low pressure side, thus enhanc‐

ing the efficiency of the air conditioner.

Note

This illustration shows a refrigerant line with inner heat exchanger

as fitted e.g. on the Golf 7, Audi A4 2008 > and Audi A5 Coupé

2008 > ⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerant

circuit .

A - Refrigerant line with internal heat exchanger

B - Channels in the refrigerant line along which hot liquid refrig‐

erant flows to the evaporator (high pressure side of refrigerant

circuit).

C - Channel in the refrigerant line through which the cold gaseous

or vaporous refrigerant flows to the air conditioner compressor

(low pressure side of refrigerant circuit).

1.2.14

Quick release couplings of refrigerant

lines

Note

♦ This illustration shows the quick-release couplings with a re‐

frigerant line with internal heat exchanger as fitted e.g. on the

Audi A4 2008 > and the Audi A5 Coupé 2008 > ⇒ Heating, air

conditioning; Rep. gr. 87 ; Refrigerant circuit (vehicle-specific

workshop manual).

♦ Removal of the refrigerant line -D- involves opening the re‐

taining ring -A- e.g. with the refrigerant line release tool ( re‐

lease tool - T40149- or removal tool - T40232- ) ⇒ Heating,

air conditioning; Rep. gr. 87 ; Refrigerant circuit (vehicle-spe‐

cific workshop manual).

♦ After removing the respective refrigerant line, the quick re‐

lease couplings -B- and -G- are to be renewed along with the

associated support ring -E- or -H- and the associated seal

-F- or -J- ⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerant

circuit (vehicle-specific workshop manual) and ⇒ Electronic

parts catalogue .

A - Retaining ring (in quick release coupling on high pressure

side)

B - Quick release coupling with retaining ring “high pressure side”

C - Refrigerant line with internal heat exchanger

D - Refrigerant line “high pressure side”

E - Support ring “high pressure side”

F - Seal “high pressure side”

G - Quick release coupling with retaining ring “low pressure side”

H - Support ring “low pressure side”

J - Seal “low pressure side”

1. Refrigerant circuit

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Air conditioning systems with refrigerant R1234yf - General information - Edition 07.2017

Note

♦ The quick release couplings come in different versions -A- and

-D-. On both versions of these quick release couplings, the

refrigerant lines -C- can be released and removed in the same

way, e.g. with refrigerant line release tool -T40149/1- ⇒ Heat‐

ing, air conditioning; Rep. gr. 87 ; Refrigerant circuit (vehicle-

specific workshop manual).

♦ For quick release coupling version -A-, the control pins -B- be‐

come visible after installing the refrigerant line -C- once the

engaged refrigerant line -C- is pulled in the direction of arrow.

♦ For quick release coupling version -D-, the refrigerant line

-C- is installed in the same way as quick release coupling

-A-. When the refrigerant line -C- on this version is pulled in

the direction of arrow following assembly, the snap ring -E-

protrudes from the quick release coupling -D-, thereby indi‐

cating that the retaining ring -F- is completely engaged with

the refrigerant line -C-. The snap ring -E- must then be re‐

moved from the refrigerant line -C-.

1.2.15

Seals

♦ These seals seal the connection points between the individual

components of the refrigerant circuit

⇒ “3.2 Refrigerant circuit seals”, page 8 .

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1.2.16

Pipes and hoses in refrigerant circuit

♦ In its pure state, R1234yf refrigerant is chemically stable and

has no corrosive effect on e.g. iron, aluminium and specially

developed plastics that are suitable for this purpose. A mixture

of refrigerant oil and R1234yf refrigerant can affect certain

metals (e.g. alloys with copper) and affect or degrade certain

hose materials and plastics. Therefore, use only genuine re‐

placement parts ⇒ Electronic parts catalogue .

♦ Only use components that are resistant to R1234yf refrigerant

and its associated refrigerant oils. Do not use components

(such as seals and hoses, which are made of plastic) that

cannot be clearly allocated ⇒ Electronic parts catalogue .

♦ The pipes and hoses are held together by threaded connec‐

tions and / or special joints ⇒ Heating, air conditioning; Rep.

gr. 87 ; Refrigerant circuit (vehicle-specific workshop manual).

♦ Renew the sealing elements (e.g. seals) between the compo‐

nents ⇒ Electronic parts catalogue .

♦ For threaded connections, observe the specified torque set‐

tings. For pressure-fit connections, use dedicated release

tools ⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerant

circuit (vehicle-specific workshop manual).

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Rep. gr.87 - Air conditioning system

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Air conditioning systems with refrigerant R1234yf - General information - Edition 07.2017

1.2.17

High-pressure safety valve

The high pressure safety valve is fitted to the air conditioner com‐

pressor or the receiver.

The valve opens at a pressure of approx. 38 bar (overpressure)

and closes again when the pressure has dropped (to approx. 35

bar).

Not all the refrigerant is lost from the system.

Note

♦ Depending on the version, a transparent plastic washer -B-

may be attached to the high pressure safety valve -A- which

breaks off as soon as the valve is actuated.

♦ Depending on the version of high pressure safety valve -A-, a

cover -C- may also be pushed onto the high pressure safety

valve -A-. Should the pressure in the refrigerant circuit actually

rise above the opening pressure of the high pressure safety

valve -A- and cause the valve to open, refrigerant will not es‐

cape in one direction but scatter through the openings -D-

beneath the cover -C- instead.

♦ If a high-pressure safety valve -A- needs to be renewed, the

specified torque for the new valve (depending on the manu‐

facturer and the version of the air conditioner compressor)

must be observed when installing. Air conditioner compres‐

sors manufactured by “Denso”, “Sanden” and “Valeo” are

equipped with an O-ring seal (currently valid torque settings

are: 10 Nm for “Denso” and “Zexel/Valeo” air conditioner com‐

pressors, and 15 Nm for “Sanden” air conditioner compres‐

sors). Air conditioner compressors manufactured by “Delphi”

are fitted with an oil seal (currently valid torque setting: 15 Nm).

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♦ Renewing seals (oil seals or O-rings) ⇒ Electronic parts cata‐

logue .

♦ If a seal (oil seal or O-ring) fitted to the high-pressure safety

valve is not available as a replacement part, the removed old

part can be reused (as an exception to the general rule of using

new seals only). The old seal, however, must always be

checked for damage prior to installation. If any damage or de‐

formation is detected on the old seal, it must be renewed with

a commercially available new part ⇒ Electronic parts cata‐

logue .

♦ After filling the refrigerant circuit, check the installed high-

pressure safety valve for leaks using e.g. an electronic leak

detector.

1. Refrigerant circuit

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Air conditioning systems with refrigerant R1234yf - General information - Edition 07.2017

1.2.18

Non-return valves

Non-return valves separate the refrigerant circuit into different

areas ⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerant circuit

(vehicle-specific workshop manual).

Note

♦ The non-return valve -3- shown in installed e.g. in the Audi Q7

e-tron ⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerant

circuit (vehicle-specific workshop manual).

♦ Non-return valves in the refrigerant circuit have a certain hold‐

ing pressure in the direction of flow (approx. 0.1 bar or

100 mbar). To ensure that the refrigerant circuit can be evac‐

uated completely (residual pressure below 5 mbar), all of the

electrically actuated valves must therefore be open.

♦ Depending on the version, the direction of flow may be indi‐

cated by a sticker.

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54

Rep. gr.87 - Air conditioning system

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Air conditioning systems with refrigerant R1234yf - General information - Edition 07.2017

1.2.19

Quick-release coupling connections in

refrigerant circuit

Service connections with Schrader valve (needle valve or push

pin)

♦ Only valves and connections resistant to R1234yf refrigerant

and the related refrigerant oils may be used.

♦ Service connections -C- and -F- in an R1234yf refrigerant cir‐

cuit are configured in such a way that service couplings cannot

be connected to service connections designed for an R134a

refrigerant circuit.

♦ Different connections (external diameter) for high pressure

and low pressure side -C- and -F-.

♦ Before removing the valves or valve inserts -B- and -E-, empty

the refrigerant circuit.

♦ Always screw on sealing caps -A- and -D- with seal -G-.

Layout in vehicle ⇒ Heating, air conditioning; Rep. gr. 87 ; Re‐

frigerant circuit (vehicle-specific workshop manual).

– Extract refrigerant before unscrewing the valves.

♦ Service connection, low pressure side -F-

♦ Service connection, high pressure side -C-

♦ Valve insert (designation: Schrader or needle valve)

♦ Sealing cap for service connection on low pressure side with

seal -A-

♦ Sealing cap for service connection on high pressure side with

seal -D-

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1. Refrigerant circuit

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Air conditioning systems with refrigerant R1234yf - General information - Edition 07.2017

Note

♦ Carefully, and no more than necessary, screw in the hand‐

wheel of the service coupling (after connecting) into the quick

release coupling adapter until the valve in the service connec‐

tion is open (observe pressure gauge; do not over-tighten

valve).

♦ Service connections in an R1234yf refrigerant circuit are con‐

figured in such a way that service couplings cannot be con‐

nected to service connections designed for an R134a

refrigerant circuit.

♦ The service connections are brazed into e.g. a refrigerant line

and therefore cannot be replaced individually.

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♦ When removing and installing valve core with refrigerant cir‐

cuit discharged, use a socket - T10364- or similar.

♦ Exercise caution when tightening the valve insert due to the

low tightening torque.

♦ There are different versions of these valves; therefore tight‐

ening torques vary. For a valve insert -C- with a VG5 thread

(5.2 x 0.7 mm, tyre valve) the tightening torque is 0.4 Nm

± 0.1 Nm; for a valve insert with an M6 x 0.75 mm thread the

tightening torque is 0.9 Nm ± 0.1 Nm, and for a valve insert

with an M8 x 1.0 mm thread the tightening torque is

2.0 Nm ± 0.2 Nm.

♦ These valve caps come in different versions, which means that

the specified torques will differ. For a valve cap with an M8 x

1 mm or M10 x 1 mm thread, the specified torque is

0.4 Nm ± 0.1 Nm respectively.

♦ These valves, valve inserts and corresponding sealing caps

come in different versions. Make sure that the correct type of

valve insert is used and allocation of the sealing caps is correct

⇒ Electronic parts catalogue .

Dimensions of service connections

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Rep. gr.87 - Air conditioning system

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Air conditioning systems with refrigerant R1234yf - General information - Edition 07.2017

♦ Valve insert -A- (different versions).

♦ Service connection -B- (different versions on high pressure

and low pressure side depending on refrigerant)

Dimensions of serv‐ Service connec‐

Service connection

ice connections -B- tion for R134a re‐ for R1234yf refriger‐

frigerant

High-

ant

Low-

High-

Low-

pressure pres‐

pressure pressure

side

sure

side

External diameter

-D1-

16.0 mm 13.0 m 17.0 mm 14.0 mm

m

External diameter

14.0 mm 11.0 m 13.0 mm 12.0 mm

m

-D2-

Shoulder -L1-

Shoulder -L2-

4.6 mm 6.15 m 9.0 mm 4.75 mm

m

8.16 mm 9.16 m 12.5 mm 7.2 mm

m

Installation position of 6.1 - 7.1 6.1 - 7.1 8.3 - 9.3 8.3 - 9.3

valve (unactuated)

-C-

mm

Service connections with primary sealing valve (ball valve)

♦ This type of service connection is currently not used in VW/

Audi refrigerant circuits.

♦ Only valves and connections resistant to R1234yf refrigerant

and the related refrigerant oils may be used.

♦ Service connections in an R1234yf refrigerant circuit are con‐

figured in such a way that service couplings cannot be con‐

nected to service connections designed for an R134a

refrigerant circuit.

♦ Different connections (external diameter) for high-pressure

and low-pressure sides.

♦ Discharge refrigerant circuit before removing valve or valve

inserts.

♦ Always screw on sealing caps with seal.

Layout in vehicle ⇒ Heating, air conditioning; Rep. gr. 87 ; Re‐

frigerant circuit (vehicle-specific workshop manual).

1. Refrigerant circuit

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Air conditioning systems with refrigerant R1234yf - General information - Edition 07.2017

Connection with high pressure valve

1 - Boss with internal thread (brazed on)

2 - Seal (version and designation: black or coloured ⇒ Elec‐

tronic parts catalogue )

3 - Valve with external thread and groove for seal (designation:

ball valve)

4 - Seal for sealing cap

5 - Sealing cap

Note

♦ Carefully, and no more than necessary, screw in the hand‐

wheel of the service coupling (after connecting) into the quick

release coupling adapter until the valve in the service connec‐

tion is open (observe pressure gauge; do not over-tighten

valve).

♦ When removing and installing the valve -3- with purged refrig‐

erant circuit, use e.g. an adapter from socket set - T10364- .

♦ These valves come in different versions (with internal or ex‐

ternal thread) and the specified torques can therefore differ.

For the valves -3- currently in use (external thread M12 x 1.5

mm) the tightening torque is 9 Nm ± 1 Nm.

♦ These valves and corresponding sealing caps come in differ‐

ent versions. Make sure that the correct type of valve is used

and allocation of the sealing caps is correct ⇒ Electronic parts

catalogue .

Connection with low pressure valve

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1 - Boss with external thread and groove for O-ring (brazed in)

2 - Seal (version and designation: black or coloured ⇒ Elec‐

tronic parts catalogue )

3 - Valve with internal thread

4 - Seal for sealing cap

5 - Sealing cap

Note

♦ Carefully, and no more than necessary, screw in the hand‐

wheel of the service coupling into the quick release coupling

adapter until the valve in the service connection is open (ob‐

serve pressure gauge; do not over-tighten valve).

♦ When removing and installing the valve -3- with purged refrig‐

erant circuit, use e.g. an adapter from socket set - T10364- .

♦ These valves come in different versions (with internal or ex‐

ternal thread) and the specified torques can therefore differ.

For the valves -3- currently in use (internal thread

M10 x 1.25 mm) the tightening torque is 9 Nm ± 1 Nm.

♦ These valves and corresponding sealing caps come in differ‐

ent versions. Make sure that the correct type of valve is used

and allocation of the sealing caps is correct ⇒ Electronic parts

catalogue .

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Rep. gr.87 - Air conditioning system

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Air conditioning systems with refrigerant R1234yf - General information - Edition 07.2017

1.2.20

Connections with valve for switches in

refrigerant circuit

Note

Refer to vehicle-specific refrigerant circuit for switching pres‐

sures, removing and installing switches and location/design of

switches ⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerant

circuit (vehicle-specific workshop manual).

•

The switches on the high pressure and low pressure sides

have different threads.

Only valves and seals resistant to R1234yf refrigerant and the

related refrigerant oils may be used ⇒ Electronic parts cata‐

logue .

A - Connection (brazed)

B - Seal

C - Valve (with seal)

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Note

♦ To remove and install the valve -C- with the refrigerant circuit

empty, use e.g. an adapter from socket set - T10364- (speci‐

fied torque ⇒ page 55 ).

♦ There are different versions of these valves; therefore tight‐

ening torques vary. For a valve insert -C- with a VG5 thread

(5.2 x 0.7 mm, tyre valve) the tightening torque is 0.4 Nm

± 0.1 Nm; for a valve insert with an M6 x 0.75 mm thread the

tightening torque is 0.9 Nm ± 0.1 Nm, and for a valve insert

with an M8 x 1.0 mm thread the tightening torque is

2.0 Nm ± 0.2 Nm.

1.2.21

Pressure senders and switches in refrig‐

erant circuit

Note

♦ Pressure senders and switches come in different versions,

with different functions and different designations ⇒ Heating,

air conditioning; Rep. gr. 87 ; Refrigerant circuit (vehicle-spe‐

cific workshop manual).

♦ Switching pressures, removing and installing switches and

switch layout and type ⇒ Heating, air conditioning; Rep. gr.

87 ; Refrigerant circuit (vehicle-specific workshop manual).

1. Refrigerant circuit

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Air conditioning systems with refrigerant R1234yf - General information - Edition 07.2017

♦ The high pressure sender shown is installed e.g. in the Golf 7

and Audi A3 ⇒ Heating, air conditioning; Rep. gr. 87 ; Re‐

frigerant circuit (vehicle-specific workshop manual).

♦ One version of pressure sender generates a square-wave sig‐

nal when voltage is applied. This signal changes with the

pressure in the system. The other version of pressure sender

exchanges information with the corresponding control unit via

data bus (e.g. via the “LIN bus”) when voltage is applied ⇒ Cur‐

rent flow diagrams, Electrical fault finding and Fitting locations

and ⇒ Vehicle diagnostic tester in “Guided Fault Finding”

mode - air conditioning system. Therefore, pay attention to the

correct version of pressure sender.

♦ The pressure senders come in different versions. Depending

on the version, they can currently only be distinguished exter‐

nally by the part number, which is why attention should be paid

during renewal to their correct allocation (part number ⇒ Elec‐

tronic parts catalogue ). Reason: These senders emit different

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signals, and the relevant control units can only evaluate the

signal to which they have been matched ⇒ Vehicle diagnostic

tester in “Guided Fault Finding” mode - air conditioning system

and ⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerant cir‐

cuit (vehicle-specific workshop manual).

♦ One version of pressure sender only transmits the measured

value for the pressure in the refrigerant circuit to the connected

control unit. The other version transmits the measured value

for the pressure in the refrigerant circuit and the measured

temperature to the connected control unit, which is why atten‐

tion should be paid to the correct version ⇒ Electronic parts

catalogue .

♦ With this signal, the downstream control units calculate the

pressure in the refrigerant circuit and actuate the radiator fans

and engine, the air conditioning system magnetic clutch - N25-

accordingly or manipulate actuation of the air conditioner com‐

pressor regulating valve - N280- ⇒ Vehicle diagnostic tester in

“Guided Fault Finding” mode - air conditioning system and ⇒

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

hicle-specific workshop manual).

1.2.22

Refrigerant pressure and temperature

sender

CAUTION

Risk of freezing injury caused by escaping pressurised refrig‐

erant.

There is a risk of injury to the skin and parts of the body due to

freezing.

– Wear protective gloves.

– Wear protective goggles.

– Extract refrigerant and open the refrigerant circuit immedi‐

ately afterwards.

– If more than 10 minutes have passed since the refrigerant

was extracted, repeat the extraction process before opening

the refrigerant circuit. Pressure could build up in the refrig‐

erant circuit from continued evaporation.

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Rep. gr.87 - Air conditioning system

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Senders for connection to a refrigerant circuit with valve

Note

♦ Refer to vehicle-specific refrigerant circuit for switching pres‐

sures, removing and installing switches and location/design of

switches ⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerant

circuit (vehicle-specific workshop manual).

♦ These senders come in different versions, with different func‐

tions and different designations. The refrigerant pressure and

temperature sender - G395- shown as follows is installed e.g.

in the Golf GTE, Audi A4, Audi Q5 and Audi Q5 Hybrid ⇒

Heating, air conditioning; Rep. gr. 87 ; Refrigerant circuit;

System overview - refrigerant circuit .

♦ Before loosening the threaded connection of the sender,

check which version of sender it is ⇒ Heating, air conditioning;

Rep. gr. 87 ; Refrigerant circuit; System overview - refrigerant

circuit .

♦ For senders designed for connection to a refrigerant circuit

without valve. The refrigerant must be extracted before the

threaded connection is loosened. If the sender is not removed

within 10 minutes after the system has been evacuated, pres‐

sure may develop in the refrigerant circuit due to re-evapora‐

tion. Extract refrigerant again.

♦ Different designations depending on the function and vehicle

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⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerant circuit;

System overview - refrigerant circuit .

♦ The sender for refrigerant pressure and refrigerant tempera‐

ture is installed e.g. in place of the high pressure sender or

pressure sender for refrigerant circuit ⇒ Heating, air condi‐

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

shop manual)

♦ The sender for refrigerant pressure and refrigerant tempera‐

ture, the pressure sender for refrigerant circuit and high pres‐

sure sender come in different versions. Depending on the

version, they can currently only be distinguished externally by

the part number, which is why attention should be paid during

renewal to their correct allocation (part number ⇒ Electronic

parts catalogue ). Reason: These senders emit different sig‐

nals, and the relevant control units can only evaluate the signal

to which they have been matched ⇒ Vehicle diagnostic tester

in “Guided Fault Finding” mode - air conditioning system and

⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerant circuit

(vehicle-specific workshop manual).

♦ The sender for refrigerant pressure and refrigerant tempera‐

ture (and the pressure sender for refrigerant circuit) exchange

information with the respective control unit via the data bus

(e.g. “LIN bus”) when voltage is applied. The respective control

units use this information to calculate the pressure and tem‐

perature in the refrigerant circuit. Any faults detected in this

way are passed on to the control unit ⇒ Vehicle diagnostic

tester in “Guided Fault Finding” mode.

♦ The sender for refrigerant pressure and refrigerant tempera‐

ture transmits the measured valve for the pressure in the

refrigerant circuit and the measured temperature to the con‐

nected control unit. The pressure sender for refrigerant circuit

only transmits the measured value for the pressure in the re‐

frigerant circuit to the connected control unit. Even though on

most vehicles only the pressure signal is evaluated, no other

pressure sender may be installed in a vehicle for which provi‐

sion is made for a refrigerant pressure and refrigerant tem‐

perature sender ⇒ Electronic parts catalogue .

1. Refrigerant circuit

61

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Air conditioning systems with refrigerant R1234yf - General information - Edition 07.2017

♦ The temperature measured by this refrigerant pressure and

lk

temperature sender deviates from the actual temperature of

the refrigerant in the refrigerant circuit owing to the design of

the sender and the fitting location. It is therefore not evaluated

at present by all control units and is used to regulate the air

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

Refrigerant circuit; System overview - refrigerant circuit (vehi‐

cle-specific workshop manual).

♦ With this information, the respective control units calculate the

pressure in the refrigerant circuit and actuate the downstream

control units (radiator fan control unit, engine control unit etc.)

via data bus. These control units subsequently actuate e.g. the

air conditioning system magnetic clutch - N25- , the radiator

fan and the engine ⇒ Vehicle diagnostic tester in “Guided Fault

Finding” mode - air conditioning system and ⇒ Heating, air

conditioning; Rep. gr. 87 ; Refrigerant circuit (vehicle-specific

workshop manual).

Senders for connection to a refrigerant circuit without valve

Note

♦ These senders come in different versions, with different func‐

tions and different designations. The sender for refrigerant

pressure and refrigerant temperature shown as follows is in‐

stalled e.g. in the Audi Q7 e-tron ⇒ Heating, air conditioning;

Rep. gr. 87 ; Refrigerant circuit; System overview - refrigerant

circuit .

♦ Different designations depending on the function and vehicle

⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerant circuit;

System overview - refrigerant circuit .

Possible designations for these senders

♦ Refrigerant pressure and temperature sender - G395- (e.g. in

e-Golf, Audi Q7 e-tron)

♦ Refrigerant pressure and temperature sender 2 - G826- (e.g.

in Audi Q7 e-tron)

♦ Refrigerant pressure and temperature sender 3 - G827- (e.g.

in Audi Q7 e-tron)

These senders -A- come in different versions that, depending on

the version, can currently only be distinguished externally by the

part number or, if the part number is the same, by the designation

label -B-, which is why when renewing them it is important to en‐

sure the correct allocation. Part number and designation ⇒

Electronic parts catalogue and ⇒ Heating, air conditioning; Rep.

gr. 87 ; Refrigerant circuit; System overview - Refrigerant circuit .

When a voltage is applied, these senders exchange information

with the respective control unit via the data bus (e.g. via “LIN

bus”). The respective control units use this information to calcu‐

late the pressure and temperature in the refrigerant circuit. Any

faults detected in this way are passed on to the control unit ⇒ Ve‐

hicle diagnostic tester in “Guided Fault Finding” mode.

With this information, the respective control unit calculates the

pressure in the refrigerant circuit and actuates the downstream

control units or components (radiator fan control unit, pumps,

valves etc.) via data bus according to the specifications ⇒ Vehicle

diagnostic tester in “Guided Fault Finding” mode and ⇒ Heating,

air conditioning; Rep. gr. 87 ; Refrigerant circuit; System overview

- refrigerant circuit (vehicle-specific workshop manual).

62

Rep. gr.87 - Air conditioning system

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Air conditioning systems with refrigerant R1234yf - General information - Edition 07.2017

1.2.23

Air conditioner compressor regulating

valve - N280-

Note

Refer to vehicle-specific refrigerant circuit for switching pres‐

sures, removing and installing switches and location/design of

switches ⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerant

circuit; System overview - refrigerant circuit .

♦ The regulating valve is fitted to the air conditioner compressor.

It is actuated, for example, by the air conditioning system con‐

trol unit - J301- , the operating and display unit for front air

conditioning system - E87- or the Climatronic control unit -

J255- (potentially also via data bus and an additional control

unit depending on the vehicle) ⇒ Vehicle diagnostic tester in

“Guided Fault Finding” mode - air conditioning system and ⇒

lk

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

hicle-specific workshop manual).

♦ The regulating valve influences the pressure on the low pres‐

sure side and thus the temperature at the evaporator.

Note

The air conditioner compressor regulating valve - N280- is an in‐

tegral part of the air conditioner compressor and cannot be re‐

newed individually on all air conditioner compressors ⇒

Electronic parts catalogue .

1.2.24

Refrigerant temperature sender

Note

♦ A refrigerant temperature sender (a temperature sender that

does not evaluate the pressures) is currently not used by

Volkswagen/Audi.

♦ Switching pressures, removing and installing switches and

switch layout and design ⇒ Vehicle diagnostic tester in “Gui‐

ded Fault Finding” mode - air conditioning system and ⇒

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

hicle-specific workshop manual).

1. Refrigerant circuit

63

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Air conditioning systems with refrigerant R1234yf - General information - Edition 07.2017

♦ The refrigerant temperature sender (with temperature-de‐

pendent resistor) is installed e.g. in the high pressure line in

the vicinity of the air conditioner compressor.

♦ There is a direct correlation between temperature and pres‐

sure in the refrigerant circuit: if there is too little refrigerant in

the refrigerant circuit, the temperature in the refrigerant circuit

rises during operation of the air conditioning system on the

high pressure side greater than permitted for this pressure.

Note

The respective control unit, e.g. the operating and display unit for

lk

front air conditioning system - E87- or the Climatronic control unit

- J255- evaluates the pressure and the temperature in the refrig‐

erant circuit and switches off the air conditioner compressor if the

temperature increases above the value stored for this pressure

⇒ Vehicle diagnostic tester in “Guided Fault Finding” mode - air

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

87 ; Refrigerant circuit (vehicle-specific workshop manual).

1.3

Possible complaints

⇒ “1.3.1 Prerequisites for investigating a complaint”, page 64

⇒ “1.3.2 Possible complaints”, page 64

⇒ “1.3.3 Odours from heater and air conditioner unit”, page 66

1.3.1

Prerequisites for investigating a com‐

plaint

•

No fault was evident during fault finding in the electrical sys‐

tem, vacuum system and air ducts/channels ⇒ Vehicle diag‐

nostic tester in “Guided Fault Finding” mode - air conditioning

system (and battery control), ⇒ Current flow diagrams, Elec‐

trical fault finding and Fitting locations and ⇒ Heating, air

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

ing output .

•

Self-diagnosis in “Guided Fault Finding” mode - air condition‐

ing system (e.g. using ⇒ Vehicle diagnostic tester in “Guided

Fault Finding” mode - air conditioning system) provides no

evidence of a complaint.

No shut-off condition for the air conditioner compressor is dis‐

played in the measured values of the control unit of the air

conditioning system ⇒ Vehicle diagnostic tester in “Guided

Fault Finding” mode - air conditioning system.

1.3.2

Possible complaints

Note

♦ For all complaints marked with *

⇒ “2.14 Checking pressures”, page 170 .

♦ If on vehicles with 2 evaporators a problem is encountered in

just one evaporator, check the pressures in the refrigerant cir‐

cuit as well ⇒ “2.14 Checking pressures”, page 170 .

♦ The cooling has failed completely.*

♦ Insufficient cooling output at all vehicle speeds and engine

speeds.*

♦ No or insufficient cooling after driving a few miles. *

64

Rep. gr.87 - Air conditioning system

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Air conditioning system -> 1.2 General description - components of refrigerant circuit for Your Volkswagen Touran 4 Door Second Generation (2015-2022)

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