Audi A4 2001 - Two-Stage ABS Return Pump Operation

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1.4.8 Refrigerant Circuit Pressures and Tem‐
peratures
Caution
♦ When performing work on refrigerant circuit, observe all
generally applicable safety precautions and pressure ves‐
sel regulations.
The pressures and temperatures in the refrigerant circuit depend
on the current operating conditions (such as engine RPM, coolant
fan level 1, 2 or 3, engine temperature, A/C compressor on or off)
as well as on the effects of outside influences (such as outside
temperature, humidity, desired cooling output).
In vehicles with A/C compressor regulator valve -N280- , the
pressure is modified on the low pressure side by the A/C com‐
pressor regulator valve.
For this reason, values indicated in the following table are valid
only as reference points. They are attained at an engine speed of
1500 to 2000 RPM and an ambient temperature of 20° C after
about 20 minutes.
The connections for the pressure gauge set intended for the pres‐
sure measurement are indicated on the vehicle specific refriger‐
ant circuit. Refer to ⇒ Heating, Ventilation and Air Conditioning;
Rep. Gr. 87 ; Diagnosis and Testing (vehicle-specific repair man‐
ual).
At 20° C with the engine not running, the pressure in the refrig‐
erant circuit is 4.7 bar. Refer to
⇒ “1.1.3 Refrigerant R134a Vapor Pressure Table“, page 4 .
Note
Pressure is measured in different units: 1 MPa (mega Pascal)
corresponds to 10 bar positive pressure or 145 psi, 1 bar absolute
pressure corresponds to 0 bar positive pressure and thus to the
ambient pressure (atmospheric pressure).
♦ Refrigerant Circuit with Expansion Valve, refer to
⇒ “2.1.13 Refrigerant Circuit with Expansion Valve, Pressures
and Temperatures“, page 69 .
♦ Refrigerant Circuit with Restrictor and Reservoir, refer to
⇒ “2.1.14 Refrigerant Circuit with Restrictor and Reservoir,
Pressures and Temperatures“, page 71 .
1.4.9 Refrigerant Circuit, Converting R12 to
R134a
CFC refrigerants are no longer used in the automotive industry.
Converting refrigerant circuits from R12 refrigerant to R134a re‐
frigerant and servicing converted circuits, refer to Repair Manual:
Air conditioner with refrigerant R12 Parts 2 and 3. This repair
manual is only available in printed form.
1.4.10 Refrigerant Circuit, Cleaning
Flush refrigerant circuit with refrigerant R 134a. Refer to
⇒ “1.4.13 Refrigerant Circuit Flushing With Refrigerant R134a“,
page 32 (or with compressed air and nitrogen, refer to
⇒ “1.4.12 Refrigerant Circuit Flushing With Compressed Air and
Nitrogen “, page 29 ) if:
Audi 100 1991 ➤ , Audi 80 1992 ➤ , Audi A1 2011 ➤ , Audi A2 2001 ➤ , A ...
Refrigerant R134a Servicing - Edition 01.2011
1. General Information 27