Get General information on refrigerant circuit -> Layout of components of refrigerant circuit and their influence on high-pressure and low pressure sides 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

3.2

Layout of components of refrigerant cir‐

cuit and their influence on high-pressure

and low-pressure sides

High-pressure side: Condenser, receiver and restrictor or expan‐

sion valve to separate the high and low-pressure liquid ends.

High pressure results from the restrictor or expansion valve form‐

ing a constriction and causing the refrigerant to build up, thus

leading to an increase in pressure and temperature.

Excess pressure occurs if too much refrigerant or refrigerant oil

is used, the condenser is contaminated, the radiator fan is defec‐

tive, the system is blocked or in the event of moisture in the

refrigerant circuit (icing-up of restrictor or expansion valve).

Low-pressure side: Evaporator, evaporator temperature sensor

and air conditioner compressor to separate the sections with high

and low gas pressure.

A drop in system pressure can be caused by a loss of refrigerant,

the restrictor or expansion valve (constrictions), a defective air

conditioner compressor or an iced-up evaporator.

30

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

⇒ “3.2.1 Mechanically driven air conditioner compressor”,

page 31

⇒ “3.2.2 Electrically driven air conditioner compressor for vehicles

with a high-voltage system”, page 32

⇒ “3.2.3 Condenser”, page 36

⇒ “3.2.4 Evaporator”, page 36

⇒ “3.2.5 Heat exchanger for heat pump operation”, page 37

⇒ “3.2.6 Fluid collector”, page 37

⇒ “3.2.7 Reservoir”, page 38

⇒ “3.2.8 Restrictor”, page 38

⇒ “3.2.9 Receiver”, page 40

⇒ “3.2.10 Expansion valve”, page 41

⇒ “3.2.11 Expansion valve with shut-off valve”, page 41

⇒ “3.2.12 Refrigerant shut-off valves”, page 42

⇒ “3.2.13 Refrigerant line with internal heat exchanger”,

page 44

⇒ “3.2.14 Quick-release couplings on refrigerant line”,

page 44

⇒ “3.2.15 O-rings”, page 46

⇒ “3.2.16 Pipes and hoses of refrigerant circuit”, page 46

⇒ “3.2.17 High-pressure safety valve”, page 46

⇒ “3.2.18 Non-return valves”, page 47

3.2.1

Mechanically driven air conditioner com‐

pressor

The air conditioner compressor is driven by the engine via a poly

V-belt or a drive shaft.

Air conditioner compressor with magnetic clutch:

♦ An electromagnetic clutch -A- attached to the air conditioner

compressor provides the power link between the pulley -B-

and the compressor crankshaft when the air conditioning is

switched on.

♦ An overload protection attached to the clutch plate or fitted in

the solenoid of the air conditioner compressor is triggered if

the air conditioner compressor is not running smoothly in order

to protect the belt drive against overload.

Air conditioner compressor with no magnetic clutch:

♦ An overload protection attached to the pulley -B- or fitted in the

drive unit of the air conditioner compressor is triggered if the

air conditioner compressor is not running smoothly in order to

protect the belt drive against overload.

All air conditioner compressors

The air conditioner compressor draws in refrigerant gas from the

evaporator, compresses it and conveys it to the condenser.

3. General information on refrigerant circuit

31

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

Air conditioner with refrigerant R134a - Edition 11.2018

Note

♦ The air conditioner compressor contains refrigerant oil which

mixes with refrigerant R134a at all temperatures.

♦ The type plate indicates the refrigerant for which the air con‐

ditioner compressor is designed. A valve regulates the pres‐

sure on the low-pressure side within the specified range

(control characteristic).

♦ At present, actuation is effected externally by way of a regu‐

lating valve -C- on air conditioner compressors with or without

magnetic clutch.

♦ On air conditioner compressors with no magnetic clutch, the

engine is only to be started following complete assembly of the

refrigerant circuit.

♦ To prevent air conditioner compressor damage if the refriger‐

ant circuit is empty, the magnetic clutch is deactivated and the

air conditioner compressor regulating valve - N280- no longer

actuated (air conditioner compressor idles with engine).

♦ If the refrigerant circuit is empty, an air conditioner compressor

with no air conditioning system magnetic clutch - N25- (with

air conditioner compressor regulating valve - N280- ) is switch‐

ed to internal lubrication by way of a valve.

♦ Depending on the version of the air conditioner compressor,

there may be a valve on the high-pressure side of the com‐

pressor which prevents liquid refrigerant from flowing back into

the compressor after the air conditioner has been switched off.

If an air conditioner compressor with such a valve is installed

in a vehicle with a refrigerant circuit with an expansion valve,

it may take a relatively long time before the pressure in the

high-pressure side drops (the expansion valve is cold and the

pressure in the low-pressure side increases rapidly after the

compressor is switched off; the expansion valve is closed and

the refrigerant can only flow slowly to the low-pressure side).

If the air conditioner compressor is switched on, the pressure

in the low-pressure side drops, the expansion valve is opened

and the refrigerant can flow to the low-pressure side.

♦ On air conditioner compressors with an electromagnetic clutch

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

is usually only activated in conjunction with regulating valve

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

cuit .

3.2.2

Electrically driven air conditioner com‐

pressor for vehicles with a high-voltage

system

Vehicles with high-voltage system (hybrid vehicles)

High voltage! Danger to life!

The voltage levels in the high-voltage system constitute a safety

hazard. Danger of severe or fatal injuries from electric shock.

– Persons with life-sustaining or other electronic medical devi‐

ces in or on their body must not perform any work on the high-

voltage system. Such medical devices include internal anal‐

gesic pumps, implanted defibrillators, pacemakers, insulin

pumps and hearing aids.

– The high-voltage system must be de-energised by a suitably

qualified person.

32

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

Risk of injury - engine may start unexpectedly

It is difficult to determine whether the drive system of an electric

vehicle or hybrid vehicle is active. Moving parts can trap or draw

in parts of the body.

– Switch off ignition.

– Place ignition key outside vehicle.

Risk of damage to high-voltage wiring

Incorrect handling may result in damage to the insulation of high-

voltage wires or high-voltage connectors.

– Never use high-voltage wiring or high-voltage connectors as

a support.

– Never prop tools against high-voltage wiring or high-voltage

connectors.

– Never bend or kink high-voltage wiring.

– Pay attention to coding when connecting high-voltage con‐

nections.

♦ For all work on vehicles with high-voltage system, note addi‐

tional warnings for working on such vehicles

⇒ “1 Warning instructions when working on vehicles with high-

voltage system”, page 1 .

♦ If work near high-voltage system components is necessary,

perform a visual check of the high-voltage components and

wires to check for damage ⇒ page 2 .

♦ If work on high-voltage system components is necessary, de-

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

high-voltage system or ⇒ Electrical 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 during test and measurement

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

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

system; General information; Rep. gr. 27 ; Charging battery

and ⇒ Electrical system; Rep. gr. 93 ; General warning in‐

structions for work on the high-voltage system .

3. General information on refrigerant circuit

33

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

Air conditioner with refrigerant R134a - Edition 11.2018

– For test and measurement 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 take care to keep well clear of the engine

when it is running. Set up any tools needed so that they cannot

come into contact with moving parts.

Electrically driven air conditioner compressor

WARNING

Danger of short circuit

The air conditioner compressor operates at up to 288 V in a

speed range between 800 and 8600 rpm.

Avoid contact with the air conditioner compressor when switch‐

ing on the ignition or starting the drive units - danger of short

circuit.

♦ The air conditioner compressor draws in refrigerant gas from

the evaporator, compresses it and conveys it to the condens‐

er.

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

plied with power by the power and control electronics for

electric drive - JX1- .

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

grated in the air conditioner compressor regulates the speed

and thereby the output of the air conditioner compressor ( elec‐

trical air conditioner compressor - V470- ) based on the re‐

quest received via the data bus ⇒ Vehicle diagnostic tester,

“Guided Fault Finding” function for air conditioner and battery

regulation .

♦ The electrically driven air conditioner compressor is not fitted

with an air conditioner compressor regulating valve - N280- .

♦ Prior to installation, check the air conditioner compressor and

bracket attachment points. The contact surfaces must be

clean and free from rust and grease. If this is not the case,

treat the contact surfaces accordingly with the contact surface

cleaning set - VAS 6410- ⇒ Electrical system; General infor‐

mation; Rep. gr. 97 ; Repairing wiring harnesses and con‐

nectors .

34

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

♦ If the control unit for air conditioning compressor - J842- is

defective, the amount of refrigerant oil in the new air condi‐

tioner compressor must be adjusted. The refrigerant circuit

does not have to be flushed with R134a.

♦ The control unit for air conditioning compressor - J842- and

the electrical air conditioner compressor - V470- form one

component and cannot be separated at present.

♦ The electrically driven air conditioner compressor is not fitted

with -N280- . The output of the air conditioner compressor is

regulated externally by way of the air conditioner compressor

speed ⇒ Current flow diagrams, Electrical fault finding and Fit‐

ting locations and ⇒ Vehicle diagnostic tester, “Guided Fault

Finding” function for air conditioner and battery regulation .

♦ At present, the electrically driven air conditioner compressor

operates on the principle of a scroll-type supercharger (similar

to the "G-Lader" supercharger).

♦ The air conditioner compressor contains refrigerant oil which

mixes with refrigerant R134a at all temperatures.

♦ The type plate indicates the refrigerant for which the air con‐

ditioner compressor is designed.

♦ The integrated electronics regulate the output of the air con‐

ditioner compressor (and thus the pressure on the low-pres‐

sure side) within the specified range (control characteristic) by

way of the speed.

♦ The engine should only be started after the refrigerant circuit

has been assembled completely.

♦ The air conditioner compressor is fitted with a secured oil sup‐

ply to prevent damage if the refrigerant circuit is empty. This

3

means that approx. 40 to 50 cm of refrigerant oil remains in

the air conditioner compressor.

♦ Like the mechanically driven air conditioner compressor, the

electrically driven air conditioner compressor has a pressure

relief valve.

♦ On vehicles with battery cooling, hybrid operation is only pos‐

sible with the air conditioner charged and with no air condi‐

tioner faults stored ⇒ Vehicle diagnostic tester, “Guided Fault

Finding” function for air conditioner and battery regulation .

♦ After installing the electrically driven air conditioner compres‐

sor and then charging the refrigerant circuit, first start up the

compressor via the “Compressor run-in” function of the basic

setting routine. Otherwise, the air conditioner compressor may

be damaged if refrigerant oil has accumulated in the compres‐

sion chamber of the air conditioner compressor due to inap‐

propriate storage prior to installation ⇒ Vehicle diagnostic

tester in “Guided Fault Finding” mode for air conditioner 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

(“Guided Fault Finding” mode for air conditioner and battery

regulation) .

3. General information on refrigerant circuit

35

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

Air conditioner with refrigerant R134a - Edition 11.2018

3.2.3

Condenser

The condenser transfers heat from the compressed refrigerant

gas to 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; Rep. gr. 87 ; Refrigerant

circuit (vehicle-specific Workshop Manual) and ⇒ Electronic

parts catalogue .

♦ 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 pay attention to the correct version and

allocation of the condenser ⇒ page 292 and ⇒ Electronic

parts catalogue .

3.2.4

Evaporator

Evaporators come in different versions. Depending on the layout

and function, the thermal energy required to evaporate the refrig‐

erant is taken from the air flowing through the evaporator (e.g. in

the case of the evaporator in the air conditioning unit or in the

battery cooling module) or the coolant flowing through the evap‐

orator (e.g. in the case of the heat exchanger for high-voltage

battery) ⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerant

circuit (vehicle-specific Workshop Manual).

Note

Two evaporator versions are described below.

36

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

Evaporator in the air conditioning unit (or in the battery cooling

module)

The liquid refrigerant evaporates in the tubes of the evaporator.

The heat required for this is extracted from the air flowing past the

evaporator fins. The air cools down. The refrigerant evaporates

and is extracted from the air conditioner compressor with the ab‐

sorbed heat.

A defined quantity of refrigerant is supplied to the evaporator by

way of a restrictor or expansion valve. In systems with an expan‐

sion valve, the flow rate is regulated so that only gaseous refrig‐

erant emerges at the evaporator outlet.

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

The liquid refrigerant evaporates in the evaporator (heat ex‐

changer). The heat required for this is extracted from the coolant

flowing through the evaporator. The coolant cools off, and the re‐

frigerant evaporates and is drawn in by the air conditioner com‐

pressor with the absorbed heat.

A specified quantity of refrigerant is supplied to the evaporator via

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

rate of the refrigerant (or coolant) is regulated so that the refrig‐

erant emerging from the evaporator outlet is in gaseous form only

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

hicle-specific Workshop Manual).

3.2.5

Heat exchanger for heat pump opera‐

tion

The refrigerant (gaseous or vaporous) compressed by the air

conditioner compressor is liquefied in the heat exchanger -A-; the

released heat is transferred to the coolant flowing through ⇒

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

specific Workshop Manual).

3.2.6

Fluid collector

In certain operating modes (e.g. in heat pump mode), the receiver

(e.g. on the condenser). is not incorporated in the refrigerant cir‐

cuit. The fluid collector -B- collects the refrigerant, stores a certain

amount of it (if not required) and then transfers it as a continuous

flow to the expansion valve (in front of the evaporator in the heater

and air conditioning unit) or to the heat exchanger in the high-

voltage system's coolant circuit ⇒ Heating, air conditioning; Rep.

gr. 87 ; Refrigerant circuit (vehicle-specific Workshop Manual).

3. General information on refrigerant circuit

37

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

Air conditioner with refrigerant R134a - Edition 11.2018

3.2.7

Reservoir

The reservoir collects the vapour and gas mixture coming from

the evaporator to ensure that the air conditioner compressor only

receives gaseous refrigerant. The vapour turns into gaseous re‐

frigerant.

Refrigerant oil entrained in the circuit does not remain in the res‐

ervoir as there is an oil extraction hole.

Any moisture which enters the refrigerant circuit during assembly

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

Gaseous refrigerant with oil is drawn in by the air conditioner

compressor.

Note

♦ Renew reservoir if refrigerant circuit has been open for a rel‐

atively long period and moisture has entered, or if renewal is

stipulated due to a specific complaint ⇒ page 272 .

♦ Do not remove sealing plugs -A- and -B- until immediately prior

to installation.

♦ If a reservoir is not sealed, the desiccant bag soon becomes

saturated with moisture and can no longer be used.

♦ When installing, observe arrow indicating direction of flow (if

applicable).

3.2.8

Restrictor

Restrictor upstream of evaporator

The restrictor creates a constriction. The restriction restricts the

flow, thus separating the refrigerant circuit into high and low-pres‐

sure sides. Upstream of the restrictor, the refrigerant is warm due

to the high pressure. Downstream of the restrictor, the refrigerant

is cold due to the low pressure. A strainer is fitted upstream of the

constriction to trap dirt. The strainer downstream of the constric‐

tion is designed to atomise the refrigerant before it enters the

evaporator.

Note

♦ Arrow -A- on restrictor faces evaporator.

♦ Always renew after opening circuit.

♦ There are different versions; observe the notes in the service

information media available ⇒ Heating, air conditioning; Rep.

gr. 87 ; Refrigerant circuit (vehicle-specific Workshop Manual)

and ⇒ Electronic parts catalogue .

Restrictor upstream of heat exchanger for high-voltage battery

(chiller)

38

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

The restrictor creates a restriction, which restricts the flow, thus

separating the refrigerant circuit into high and low-pressure sides.

Upstream of the restrictor, the refrigerant is warm due to the high

pressure. Downstream of the restrictor, the refrigerant 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 restrictor hole -B- is approx. 0.7 mm. De‐

pending on the version of the refrigerant line, the restrictor is

either only inserted or fixed in position in the refrigerant line. If

it is inserted, there may be a strainer for separating float ele‐

ments, which may block off the restrictor hole.

♦ Prior to installation, check for dirt, and clean or renew the

component as necessary.

♦ There are different versions; observe the notes in the service

information media available ⇒ Heating, air conditioning; Rep.

gr. 87 ; Refrigerant circuit (vehicle-specific Workshop Manual)

and ⇒ Electronic parts catalogue .

3. General information on refrigerant circuit

39

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

Air conditioner with refrigerant R134a - Edition 11.2018

3.2.9

Receiver

The receiver collects the droplets of liquid and conveys them in a

continuous stream to the expansion valve. Any moisture ingress‐

ing into the refrigerant circuit during assembly is collected by a

dryer in the receiver.

Note

♦ Renew receiver if refrigerant circuit has been open for a rela‐

tively long period and moisture has entered, or if renewal is

stipulated due to a specific complaint ⇒ page 272 .

♦ Do not remove sealing plugs until just before installation.

♦ If the receiver is not sealed, the desiccant bag soon becomes

saturated with moisture and thus unusable.

♦ When installing, observe arrow indicating direction of flow (if

applicable).

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

may also be attached to the condenser or integrated in the

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

erant circuit (vehicle-specific Workshop Manual) and ⇒ Elec‐

tronic parts catalogue .

♦ The procedure for dealing with problems differs depending on

the version of the receiver / desiccant cartridge. If, for example,

the receiver is attached to the condenser, it can be renewed

together with the desiccant cartridge. If, for example, the re‐

ceiver is integrated into the condenser, it is usually possible to

renew the desiccant cartridge and any additional filter element

separately. If the receiver is integrated into the condenser and

it is not possible to renew the receiver/desiccant cartridge

separately, it may be necessary to renew the entire condenser

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

(vehicle-specific Workshop Manual) and ⇒ Electronic parts

catalogue .

♦ Depending on the design of the refrigerant circuit, the desic‐

cant bag (desiccant cartridge) may also be installed in the

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

erant circuit (vehicle-specific Workshop Manual) and ⇒ Elec‐

tronic parts catalogue .

40

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

3.2.10

Expansion valve

The expansion valve atomises the refrigerant flowing in and con‐

trols the flow rate according to the heat transfer so that it does not

vaporise before reaching the evaporator outlet.

Note

♦ Pay attention to the correct part number on renewing the ex‐

pansion valve. ⇒ Electronic parts catalogue

♦ Different characteristic curves are matched to the relevant cir‐

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