Get Checking pressures -> Checking pressures - vehicles with restrictor and reservoir (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

Vehicles with electrical air conditioner compressor - V470- (vehi‐

cles with high-voltage system)

If the drive system is active but the electrical air conditioner com‐

pressor is not activated:

– Check activation of air conditioner compressor via corre‐

sponding control unit ⇒ Heating, air conditioning; Rep. gr. 87 ;

Refrigerant circuit (vehicle-specific Workshop Manual) and

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

All vehicles

♦ Checking pressures on vehicles with a restrictor and reservoir

(with internally regulated air conditioner compressor)

⇒ page 201

♦ Checking pressures on vehicles with an expansion valve and

receiver (with internally regulated air conditioner compressor)

⇒ page 206

♦ Checking pressures on vehicles with restrictor, reservoir and

air conditioner compressor regulating valve - N280- (with ex‐

ternally regulated air conditioner compressor) ⇒ page 212

♦ Checking pressures on vehicles with expansion valve, receiv‐

er and air conditioner compressor regulating valve - N280-

(with externally regulated air conditioner compressor)

⇒ page 219

♦ Check pressures on vehicles with electrically driven air con‐

ditioner compressor (Audi A3 e-tron, Audi Q5 hybrid, Audi Q7

e-tron etc.) ⇒ page 230 .

8.2

Checking pressures - vehicles with re‐

strictor and reservoir (with internally

regulated air conditioner compressor)

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.

8. Checking pressures

201

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

Air conditioner with refrigerant R134a - Edition 11.2018

Note

♦ Switching pressures for refrigerant circuit switches are vehi‐

cle-specific.

♦ The port with a valve for the low-pressure switch or on the

evaporator should only be used where the vehicle does not

have a service port on the low-pressure side and access to the

port on the air conditioning system compressor or reservoir is

not possible (measurement accuracy). Only applies for certain

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

circuit (vehicle-specific Workshop Manual).

⇒ “8.2.1 Specifications for pressures in refrigerant circuit”,

page 202

8.2.1

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 (measured at service connection) in bar

B - Low pressure (measured at connection with valve at air con‐

ditioner compressor or at reservoir) in bar

C - Permissible tolerance range

D - Low pressure (measured at connection with valve for low-

pressure switch or at service connection) in bar

E - Permissible tolerance range

Possible deviation from specification

Possible causes of fault

Fault elimination

•

High pressure remains constant Not enough refrigerant in circuit – Localise leak with leak detector

or only increases slightly (above

pressure with engine stopped)

and eliminate.

– Re-charge refrigerant circuit.

•

Low pressure quickly drops to

value in graph or below

Required cooling output is not at‐

tained.

•

High pressure normal

Low pressure in line with value in

graph

•

Required cooling output is not at‐

tained.

202

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 normal

Low pressure too low (see graph)

Required cooling output is not at‐

tained.

Note

If no fault is found for this problem, clean refrigerant circuit (by

flushing with refrigerant R134a ⇒ page 100 or blowing out with

compressed air and nitrogen ⇒ page 95 ).

Possible deviation from specification

Possible causes of fault

Fault elimination

•

High pressure does not rise or

only rises slightly above the pres‐

sure with the engine stopped.

♦ No actuation of the air condi‐ – Check actuation and drive of the

tioner compressor (magnetic

clutch).

air conditioner compressor and

perform repair ⇒ Heating, air

conditioning; Rep. gr. 87 ; Air

conditioner compressor (vehi‐

cle-specific Workshop Manual).

•

Low pressure does not drop or ♦ The air conditioner compressor

only drops slightly.

is not driven.

Required cooling output is not at‐

tained.

♦ Constriction or blockage in re‐ – Clean refrigerant circuit (flush

frigerant circuit (e.g. in refriger‐

ant line between service con‐

nection on low-pressure side

and air conditioner compres‐

sor).

with refrigerant R134a

⇒ page 100 or blow out with

compressed air and nitrogen

⇒ page 95 ).

– Renew hose or pipe if kinked or

constricted.

♦ Air conditioner compressor de‐ – Renew air conditioner compres‐

fective sor.

8. Checking pressures

203

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 above Constriction or blockage in refrig‐ – Run hand over refrigerant circuit

specification

erant circuit

to check for differences in tem‐

perature ⇒ Heating, air condi‐

tioning; Rep. gr. 87 ; Refrigerant

circuit (vehicle-specific Work‐

shop Manual).

Low pressure quickly drops to

value in graph or below

Required cooling output is not at‐

tained.

•

If there is a difference in temper‐

ature at one component:

– Renew hose or pipe if kinked or

constricted.

– In the event of clogging, clean

refrigerant circuit (flush with re‐

frigerant R134a ⇒ page 100 or

blow out with compressed air

and nitrogen ⇒ page 95 ).

•

If no fault is found:

– Clean refrigerant circuit (flush

with refrigerant R134a

⇒ page 100 or blow out with

compressed air and nitrogen

⇒ page 95 ).

•

High and low pressure normal at Moisture in refrigerant circuit

first

– Check and if necessary renew

reservoir (with dryer) and re‐

strictor, then evacuate refriger‐

ant circuit for at least 3 hours

(see note).

High pressure rises above speci‐

fied value

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 lon‐

ger attained.

•

High and low pressure normal at

first

After lengthy operating period,

low pressure drops excessively

(evaporator ices up)

Note

♦ 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.

♦ 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.

204

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 normal

Air conditioner compressor defective

– Clean refrigerant cir‐

cuit (flush with refrig‐

erant R134a

Low pressure too low (see graph)

⇒ page 100 or blow

out with compressed

air and nitrogen

Required cooling output is at‐

tained.

⇒ page 95 ).

– Renew air condition‐

er compressor.

Note

♦ Observe the following regarding fault “High pressure normal,

low pressure too low”: This fault may cause the evaporator to

ice up or the low-pressure switch - F73- to shut off the air con‐

ditioner compressor although the amount of refrigerant in the

circuit is OK.

♦ On the Audi 100, Audi A6 (up to and including model year

1997) and Audi V8, this fault may result in the air conditioner

compressor being shut off by the operating and display unit (if

the temperature at the fresh air blower drops below -3 °C) ⇒

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

hicle-specific Workshop Manual) or ⇒ Heating, air condition‐

ing; Rep. gr. 87 ; Overview of fitting locations - air conditioner

(vehicle-specific Workshop Manual).

Possible deviation from specification

Possible causes of fault

Fault elimination

•

High pressure normal or too high Too much refrigerant in circuit

– Extract refrigerant

from refrigerant cir‐

cuit.

Low pressure too high (see

graph)

•

If quantity of refriger‐

ant extracted roughly

corresponds to

•

Noise from air conditioner com‐

pressor (particularly after being

switched on)

specified capacity:

Required cooling output is not at‐

tained.

– Renew air condition‐

er compressor.

•

The quantity of re‐

frigerant extracted is

significantly greater

than the prescribed

charge quantity.

– Re-charge refriger‐

ant circuit.

– Repeat test.

8. Checking pressures

205

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Checking pressures -> Checking pressures - vehicles with restrictor and reservoir (with internally regulated air conditioner compressor) for Your Audi A2 SUV 1999-2005

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