Get General information on refrigerant circuit -> Pressures and temperatures in refrigerant circuit 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

3.6.10

Refrigerant temperature sender - G454-

The refrigerant temperature sender (with a temperature-sensitive

resistor) is installed, for example, in the high-pressure line near

the air conditioner compressor (only for certain vehicles manu‐

factured within a specific period, e.g. on Audi Q7 2007>).

In the refrigerant circuit, there is a direct relationship between

temperature and pressure. If there is insufficient refrigerant in the

circuit, the temperature in the refrigerant circuit during air condi‐

tioner operation will increase more sharply than envisaged for this

pressure.

Note

♦ Installed e.g. in Audi Q7 with certain engines ⇒ Heating, air

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

Workshop Manual) and ⇒ Current flow diagrams, Electrical

fault finding and Fitting locations.

♦ The operating and display unit ( Climatronic control unit -

J255- ) evaluates the pressure and the temperature in the

refrigerant circuit and switches off the air conditioner com‐

pressor if the temperature increases above the value stored

for this pressure ⇒ Heating, air conditioning; Rep. gr. 87 ;

Refrigerant circuit (vehicle-specific Workshop Manual) and ⇒

Vehicle diagnostic tester (“Self-diagnosis” or “Guided Fault

Finding” function for air conditioner).

3.7

Electrical components not installed in

refrigerant circuit

⇒ “3.7.1 Radiator fan control unit J293 ”, page 65

3.7.1

Radiator fan control unit - J293-

This control unit switches the magnetic clutch and thus the air

conditioner compressor on and off. It switches the radiator fans

and calculates the pressure in the refrigerant circuit on vehicles

with a high-pressure sender - G65- . Refer to ⇒ Current flow dia‐

grams, Electrical fault finding and Fitting locations and ⇒ Heating,

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

Workshop Manual).

3.8

Pressures and temperatures in refriger‐

ant circuit

Caution

♦ When working on the refrigerant circuit, observe generally

valid safety precautions and pressure vessel regulations.

The pressures and temperatures in the refrigerant circuit depend

on the instantaneous operating statuses (e.g. engine speed, ra‐

diator fan speed 1, 2, or 3, engine temperature, air conditioner

compressor on or off) as well as environmental influences (e.g.

ambient temperature, humidity, required cooling output).

3. General information on refrigerant circuit

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

Air conditioner with refrigerant R134a - Edition 11.2018

On vehicles with air conditioner compressor regulating valve -

N280- the pressure on the low-pressure side is altered by actuat‐

ing -N280- .

On vehicles with an electrical air conditioner compressor - V470- ,

the pressure in the refrigerant circuit (high-pressure and low-

pressure sides) is regulated via the speed of the air conditioner

compressor.

On vehicles with an electrical air conditioner compressor - V470-

where the air conditioner is used not only to cool the passenger

compartment but also to cool high-voltage system components

and as a heat pump to heat the passenger compartment, different

conditions, pressures and temperatures apply in the refrigerant

circuit (e.g. on the Audi Q7 e-tron) ⇒ Vehicle diagnostic tester in

“Guided Fault Finding” mode and ⇒ Heating, air conditioning;

Rep. gr. 87 ; Refrigerant circuit (vehicle-specific Workshop Man‐

ual).

For this reason, the values given in the following table are for ref‐

erence only. They are attained at an engine speed of 1500 to 2000

rpm and an ambient temperature of 20 °C after about 20 minutes.

Refer to the vehicle-specific refrigerant circuit for the locations of

the pressure gauge connections ⇒ Heating, air conditioning; Rep.

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

At 20 °C with the engine not running, the pressure in the refrig‐

erant circuit is 4.7 bar ⇒ page 8 (vapour pressure table).

Note

Pressure can be measured in various units: 1 MPa (megapascal)

is equivalent to 10 bar gauge pressure, or 145 psi; 1 bar absolute

pressure is the same as 0 bar gauge pressure, which is roughly

equivalent to atmospheric pressure.

⇒ “3.8.1 Refrigerant circuit with expansion valve”, page 66

⇒ “3.8.2 Refrigerant circuit with restrictor and reservoir”,

page 68

3.8.1

Refrigerant circuit with expansion valve

Note

Only applies with restrictions to vehicles with an electrical air con‐

ditioner compressor - V470- .

HP – High-pressure side of refrigerant circuit (HD in illustration)

LP – Low-pressure side of refrigerant circuit (ND in illustration)

Component

State of refrigerant

Pressure (bar)

Temperature in degrees

centigrade

-1- Evaporator, from inlet Vapour

to outlet

approx. 1.2 bar¹⁾1

approx. -7 °C ²⁾2

-2- Expansion valve

Liquid, expanded to va‐ approx. 14 bar

approx. +55 °C (high-

pressure side), reduced

to -7 °C (low-pressure

side)

pour

-3- High-pressure switch / Liquid

high-pressure sender

approx. 14 bar

approx. +55 °C

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

Component

State of refrigerant

Liquid

Pressure (bar)

approx. 14 bar

Temperature in degrees

centigrade

-4- Service connection

(high-pressure side)

and

approx. +55 °C

-5- Receiver

-6- Condenser

From gas (at inlet) via va‐ approx. 14 bar

pour to liquid (at outlet)

From approx. +65 °C (at

inlet) to approx. +55 °C

(at outlet)

-7- High-pressure safety Gas

valve

approx. 14 bar

approx. +65 °C

and

-8- Air conditioner com‐

pressor (HP side)

-9- Air conditioner com‐

pressor (low-pressure

side)

Gas

approx. 1.2 bar¹⁾1

approx. -1 °C ²⁾2

-10- Damping chamber

(not fitted on all vehicles)

and

-11- Service connection

(low-pressure side)

1) 1 - The pressure in a refrigerant circuit with a regulating air conditioner compressor is maintained at approx. 2 bar absolute (corresponding

to approx. 1 bar gauge) despite varying heat transfer and fluctuating engine speeds. This applies however only within the rated range of

the air conditioner compressor; if the rated range of the air conditioner compressor is exceeded, the pressure will increase

⇒ page 193 .

2) 2 - The temperature in a refrigerant circuit with a regulating air conditioner compressor is maintained within the regulating range of the

air conditioner compressor despite varying heat transfer and fluctuating engine speeds. This however only applies within the output range

of the air conditioner compressor. If the output limits of the air conditioner compressor are exceeded, the temperature will increase

⇒ page 193 .

Note

♦ Non self-regulating air conditioner compressors are switched

off by the relevant control unit via the air conditioner compres‐

sor regulating valve - N280- at evaporator temperatures below

0 °C.

♦ On vehicles with air conditioner compressor regulating valve -

N280- the pressure on the low pressure side is altered by

actuating the valve.

♦ On vehicles with two evaporators and two expansion valves,

the temperature and the pressure in the refrigerant circuit cor‐

respond to those on vehicles with only one evaporator and one

expansion valve (parallel connection).

♦ Depending on the version of the refrigerant circuit, a compo‐

nent with internal heat exchanger may be fitted (e.g. a refrig‐

erant line with internal heat exchanger is installed in the Audi

A4 2008 > and in the Audi A5 Coupé 2008 >). In the internal

heat exchanger, the hot refrigerant (liquid) flowing through the

high-pressure side gives off energy to the cold refrigerant

(gaseous or vaporous) flowing through the low-pressure side,

thus enhancing the efficiency of the air conditioner

⇒ page 44 .

Arrows show direction of refrigerant flow.

HP – High-pressure side of refrigerant circuit (HD in illustration)

LP – Low-pressure side of refrigerant circuit (ND in illustration)

3. General information on refrigerant circuit

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

Air conditioner with refrigerant R134a - Edition 11.2018

1 - Evaporator

2 - Expansion valve

3 - High-pressure switch / high-

pressure sender

❑ Different versions de‐

pending on vehicle

4 - Service connection (high-

pressure side)

5 - Receiver

❑ Different versions de‐

pending on vehicle

6 - Condenser

7 - High-pressure safety valve

8 - Air conditioner compressor

(high-pressure side)

9 - Air conditioner compressor

(low-pressure side)

10 - Damping chamber

❑ Not fitted on all vehicles

11 - Service connection (low-

pressure side)

3.8.2

Refrigerant circuit with restrictor and

reservoir

HP – High-pressure side of refrigerant circuit (HD in illustration)

LP – Low-pressure side of refrigerant circuit (ND in illustration)

Component

State of refrigerant

Gas

Pressure (bar)

Up to 20 bar

Temperature in degrees

centigrade

-1- Air conditioner com‐

pressor (high-pressure

side)

Up to +70 °C

-2- Condenser

From gas to vapour to liq‐ Up to 20 bar

uid

Up to +70 °C

-3- Restrictor

From liquid to vapour

HP side up to 20 bar, LP HP end up to +60 °C LP

side greater than 1.0 bar end warmer than -4 °C

-4- Evaporator

-5- Reservoir

-6- Air conditioner com‐

pressor (low-pressure

side)

From vapour to gas

Gas

Greater than 1.0 bar

Warmer than -4 °C

The pressures on the low-pressure side are maintained at approx.

2 bar absolute (corresponding to approx. 1 bar gauge) by the

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

“regulating” air conditioner compressor even at varying engine

speeds. This applies however only within the rated range of the

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

tioner compressor is exceeded, the pressure will increase

⇒ page 193 .

Note

On vehicles with air conditioner compressor regulating valve -

N280- the pressure on the low pressure side is altered by actuat‐

ing the valve.

Arrows show direction of refrigerant flow.

HP – High-pressure side of refrigerant circuit (HD in illustration)

LP – Low-pressure side of refrigerant circuit (ND in illustration)

1 - Air conditioner compressor

(high-pressure side)

2 - Condenser

3 - Restrictor

4 - Evaporator

5 - Reservoir

6 - Air conditioner compressor

(low-pressure side)

3. General information on refrigerant circuit

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General information on refrigerant circuit -> Pressures and temperatures in refrigerant circuit for Your Audi A2 SUV 1999-2005

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