Get Checking pressures -> Checking pressures - vehicles with expansion valve and receiver (with internally regulated air conditioner compressor) Guide for Audi A2 SUV 1999-2005

Audi 100 1991 ➤ , Audi 80 1992 ➤ , Audi A1 2011 ➤ , Audi A1 Sportback 2 ...

Air conditioner with refrigerant R134a - Edition 11.2018

Possible deviation from specification

Possible causes of fault

Fault elimination

•

High and low pressure normal

Too much refrigerant oil in circuit

– Discharge refriger‐

ant circuit.

Required cooling output is not at‐

tained.

– Clean refrigerant

circuit (flush with re‐

frigerant R134a

⇒ page 100 or blow

out with com‐

pressed air and ni‐

trogen ⇒ page 95 ).

•

High and low pressure normal

Noise from air conditioner com‐

pressor (particularly after being

switched on)

•

Required cooling output is at‐

tained.

Note

♦ Overfilling with refrigerant oil may occur if, for example, the air

conditioner compressor has been renewed without adjusting

the quantity of refrigerant oil.

♦ If there is too much refrigerant oil in the circuit, discharge the

air conditioner compressor and renew the receiver. After

cleaning the refrigerant circuit (flush with refrigerant R134a

⇒ page 100 or blow out with compressed air and nitrogen

⇒ page 95 ), add the correct amount of refrigerant oil to the

circuit ⇒ page 333 .

8.3

Checking pressures - vehicles with ex‐

pansion valve and receiver (with inter‐

nally regulated air conditioner compres‐

sor)

Note

♦ Connect air conditioner service station ⇒ page 187 .

♦ Observe test requirements ⇒ page 193 .

– Check the pressures in the refrigerant circuit (with the air con‐

ditioner service station) with the ignition switched off

⇒ page 195 .

The pressures with the ignition switched off correspond to the

specifications.

– Start engine.

– Set engine speed to 2000 rpm.

– Observe the pressure reading (e.g. pressure gauge) of the air

conditioner service station.

206

Rep. gr.87 - Air conditioning system

Audi 100 1991 ➤ , Audi 80 1992 ➤ , Audi A1 2011 ➤ , Audi A1 Sportback 2 ...

Air conditioner with refrigerant R134a - Edition 11.2018

Note

♦ Switching pressures and design of refrigerant circuit switches

are vehicle-specific.

♦ Measure the pressures at the service connections; the fitting

locations of these connections are vehicle-specific ⇒ Heating,

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

cific Workshop Manual).

⇒ “8.3.1 Specifications for pressures in refrigerant circuit”,

page 207

8.3.1

Specifications for pressures in refriger‐

ant circuit

High-pressure side:

Increasing from initial pressure (when connecting pressure

gauges) up to max. 20 bar

Low-pressure side:

Decreasing from initial pressure (on connecting pressure gauges)

to value in graph

A - High pressure in bar

B - Low pressure in bar

C - Permissible tolerance range

Possible deviation from

specification

Possible causes of fault

Fault elimination

•

High pressure remains Not enough refrigerant in circuit or – Extract refrigerant from refrigerant cir‐

constant or only increa‐ expansion valve defective

cuit.

ses slightly (above pres‐

sure with engine stop‐

ped)

•

If quantity of refrigerant extracted rough‐

ly corresponds to specified capacity:

•

Low pressure quickly

drops to value in graph

or below

– Renew expansion valve.

– Re-charge refrigerant circuit.

– Repeat test.

Required cooling output

is not attained.

•

The quantity of refrigerant extracted is

substantially less than the specified ca‐

pacity.

•

High pressure normal

Low pressure in line with

value in graph

– Locate leak with leak detector and repair

it.

•

Required cooling output

is not attained.

– Re-charge refrigerant circuit.

– Repeat test.

8. Checking pressures

207

Audi 100 1991 ➤ , Audi 80 1992 ➤ , Audi A1 2011 ➤ , Audi A1 Sportback 2 ...

Air conditioner with refrigerant R134a - Edition 11.2018

Note

If no fault can be found and air conditioner operation is not OK

when the test is repeated, clean the refrigerant circuit (flush with

refrigerant R134a ⇒ page 100 or blow out with compressed air

and nitrogen ⇒ page 95 ).

Possible devia‐ Possible causes of

Fault elimination

tion from speci‐

fication

fault

•

High pres‐ ♦ No actuation of – Check actuation and

sure does

not rise or

only rises

slightly

the air condition‐

er compressor

(magnetic

drive of the air condi‐

tioner compressor

and perform repair ⇒

Heating, air condi‐

tioning; Rep. gr. 87 ;

Air conditioner com‐

pressor (vehicle-spe‐

cific Workshop Man‐

ual).

clutch)

above the

pressure

with the en‐

gine stop‐

ped.

♦ The air condi‐

tioner compres‐

sor is not driven.

•

Low pres‐

sure does

not drop or

only drops

slightly.

Required

cooling out‐

put is not at‐

tained.

♦ Constriction or – Clean refrigerant cir‐

blockage in re‐

frigerant circuit

(e.g. in refriger‐

ant line between

service connec‐

tion on low-pres‐

sure side and air

cuit (flush with refrig‐

erant R134a

⇒ page 100 or blow

out with compressed

air and nitrogen

⇒ page 95 ).

conditioner com‐ – Renew hose or pipe if

pressor).

kinked or constricted.

♦ Air conditioner

compressor de‐

fective

– Renew air condition‐

er compressor.

208

Rep. gr.87 - Air conditioning system

Audi 100 1991 ➤ , Audi 80 1992 ➤ , Audi A1 2011 ➤ , Audi A1 Sportback 2 ...

Air conditioner with refrigerant R134a - Edition 11.2018

Possible deviation from

specification

Possible causes of fault

Fault elimination

•

High pressure increases ♦ Constriction or blockage in refriger‐ – Run hand over refrigerant circuit to

above specification

ant circuit

check for differences in tempera‐

ture ⇒ Heating, air conditioning;

Rep. gr. 87 ; Refrigerant circuit;

System overview - refrigerant cir‐

cuit (vehicle-specific Workshop

Manual).

Low pressure quickly

drops to value in graph

or below

♦ Expansion valve defective

•

Required cooling output

is not attained.

•

If there is a difference in tempera‐

ture at one component:

– Renew hose or pipe if kinked or

constricted.

– In the event of clogging, clean re‐

frigerant circuit (flush with refriger‐

ant R134a ⇒ page 100 or blow out

with compressed air and nitrogen

⇒ page 95 and renew expansion

valve if applicable).

•

If no fault is found:

– Clean refrigerant circuit (flush with

refrigerant R134a ⇒ page 100 or

blow out with compressed air and

nitrogen ⇒ page 95 and renew ex‐

pansion valve if applicable).

– Repeat test.

Note

If operation is not OK after cleaning the refrigerant circuit (flushing

with refrigerant R134a ⇒ page 100 or blowing out with com‐

pressed air and nitrogen ⇒ page 95 ), renew the expansion valve.

Possible deviation from

specification

Possible causes of fault

Fault elimination

•

High and low pressure ♦ Expansion valve defective

– Renew receiver (with dryer) and

evacuate refrigerant circuit for at

least 3 hours (see notes).

normal at first

♦ Moisture in refrigerant circuit

After some time, high

pressure increases

– Check expansion valve for dirt or

corrosion and renew if necessary

above specification and

low pressure drops to

value in graph or below

– Clean refrigerant circuit (flush with

refrigerant R134a ⇒ page 100 or

blow out with compressed air and

nitrogen ⇒ page 95 ).

•

Required cooling output

is no longer attained.

•

High and low pressure

normal at first

After lengthy operating

period, low pressure

drops excessively

(evaporator ices up)

8. Checking pressures

209

Audi 100 1991 ➤ , Audi 80 1992 ➤ , Audi A1 2011 ➤ , Audi A1 Sportback 2 ...

Air conditioner with refrigerant R134a - Edition 11.2018

Note

♦ It is not initially necessary to clean the refrigerant circuit (flush

with refrigerant R134a ⇒ page 100 or blow out with com‐

pressed air and nitrogen ⇒ page 95 ) when this problem

occurs. Normally, there is only a small quantity of moisture in

the system which can be removed by lengthy evacuation.

♦ If an issue involving moisture in the refrigerant circuit only oc‐

curs after a lengthy operating period or only infrequently (low

pressure drops below specified value and evaporator ices up),

it is sufficient to renew the dryer (adjust quantity of refrigerant

oil). Subsequently, evacuate refrigerant circuit for at least 3

hours.

Possible deviation from specifica‐

tion

Possible causes of fault

Fault elimination

•

High pressure normal or too

high

♦ Too much refrigerant in circuit – Extract refrigerant from refrigerant

circuit.

♦ Expansion valve or air condi‐

Low pressure too high (see

graph)

tioner compressor defective.

•

If amount of refrigerant extracted

roughly corresponds to specified

capacity:

Required cooling output is not

attained

– Renew expansion valve.

– Re-charge refrigerant circuit.

– Repeat test.

Air conditioner compressor

noise (particularly after switch-

on).

•

The quantity of refrigerant extrac‐

ted is significantly greater than the

prescribed charge quantity.

– Re-charge refrigerant circuit.

– Repeat test.

Note

If operation of the air conditioning system is not OK when the test

is repeated, re-fit the old expansion valve and clean the refriger‐

ant circuit (flush with refrigerant R134a ⇒ page 100 or blow out

with compressed air and nitrogen ⇒ page 95 ). Then renew the

air conditioner compressor and receiver.

Possible deviation from specifica‐

tion

Possible causes of fault

Fault elimination

•

High pressure only increases Air conditioner compressor de‐ – Clean refrigerant circuit (flush with

slightly above pressure with

engine stopped

fective

refrigerant R134a ⇒ page 100 or

blow out with compressed air and

nitrogen ⇒ page 95 ).

•

Low pressure only drops slight‐

ly

– Renew the air conditioner com‐

pressor and receiver.

Required cooling output is not

attained.

210

Rep. gr.87 - Air conditioning system

Audi 100 1991 ➤ , Audi 80 1992 ➤ , Audi A1 2011 ➤ , Audi A1 Sportback 2 ...

Air conditioner with refrigerant R134a - Edition 11.2018

Possible deviation from specifica‐

tion

Possible causes of fault

Fault elimination

•

High pressure normal

Expansion valve or air condition‐ – Renew expansion valve.

er compressor defective.

•

Low pressure too low (see

graph)

– Re-charge refrigerant circuit.

– Repeat test.

•

Required cooling output is at‐

tained.

Note

♦ If operation of the air conditioning system is not OK when the

test is repeated, re-fit the old expansion valve and clean the

refrigerant circuit (flush with refrigerant R134a ⇒ page 100 or

blow out with compressed air and nitrogen ⇒ page 95 ). Then

renew the air conditioner compressor and receiver.

♦ In this case, the evaporator may ice up although the amount

of refrigerant in the refrigerant circuit is OK.

Possible deviation from specifica‐

tion

Possible causes of fault

Fault elimination

•

High and low pressure normal Too much refrigerant oil in circuit – Discharge refrigerant circuit.

Required cooling output is not

attained.

– Clean refrigerant circuit (flush with

refrigerant R134a ⇒ page 100 or

blow out with compressed air and

nitrogen ⇒ page 95 ).

•

High and low pressure normal

Noise from air conditioner com‐

pressor (particularly after being

switched on)

•

Required cooling output is at‐

tained.

Note

♦ Overfilling with refrigerant oil may occur if, for example, the air

conditioner compressor has been renewed without adjusting

the quantity of refrigerant oil.

♦ If there is too much refrigerant oil in the circuit, discharge the

air conditioner compressor and renew the receiver. After

cleaning the refrigerant circuit (flush with refrigerant R134a

⇒ page 100 or blow out with compressed air and nitrogen

⇒ page 95 ), add the correct amount of refrigerant oil to the

circuit ⇒ page 333 .

8. Checking pressures

211

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