Audi Q5 2008 - Removal and Installation; 5.1 Leaking or Damaged Components Except A;C Compressor, Accumulator or Receiver - Circuit Empty of Refrigerant

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Note
♦ It is not initially necessary to clean the refrigerant circuit (flush
using refrigerant R134a, refer to
⇒ “1.4.13 Refrigerant Circuit Flushing With Refrigerant
R134a“, page 32 or blow through using compressed air and
nitrogen, refer to
⇒ “1.4.12 Refrigerant Circuit Flushing With Compressed Air
and Nitrogen “, page 29 ) when this problem occurs since nor‐
mally there is only a small quantity of moisture in the system
which can be removed by lengthy evacuation.
♦ If problem involving moisture in refrigerant circuit only occurs
after a lengthy operating period or only infrequently (low pres‐
sure drops below specification and evaporator ices up), it is
sufficient to replace the dryer installed in receiver (adjust quan‐
tity of refrigerant oil). Refrigerant circuit is then to be evacuated
for at least 3 hours.
♦ With this malfunction, evaporator may ice up although quantity
of refrigerant in circuit is OK.
♦ Problem with Evaporator Vent Temperature Sensor -G263-
can also cause icing-up of refrigerant circuit. If this problem is
encountered, also pay attention to measured value of evapo‐
rator vent temperature sensor using Vehicle Diagnosis, Test‐
ing & Information System -VAS5051B- (“OBD“ or “Guided
Fault Finding for the A/C System“ and ⇒ Heating, Ventilation
and Air Conditioning; Rep. Gr. 87 ; Diagnosis and Testing
(vehicle-specific repair manual).
Possible deviation from speci‐
fication
Possible cause of fault Corrective action
• High pressure normal
• Low pressure too low (see
graph)
• The required cooling per‐
formance is obtained
♦ Actuation of A/C compressor regulator
valve -N280- malfunctioning
♦ Expansion valve or A/C compressor
faulty.
♦ A/C compressor faulty.
– Check the A/C compressor
regulator valve activation.
– Clean refrigerant circuit
(flush with refrigerant R134a,
refer to
⇒ “1.4.13 Refrigerant Circuit
Flushing With Refrigerant
R134a“, page 32 or blow
through with compressed air
and nitrogen, refer to
⇒ “1.4.12 Refrigerant Circuit
Flushing With Compressed
Air and Nitrogen “, page 29 )
(not always necessary, refer
to notes).
– Replace expansion valve
and receiver
– Charge the refrigerant circuit
– Repeat test, if function is not
OK:
– Replace A/C compressor.
– Charge the refrigerant circuit
– Repeat test
Audi 100 1991 ➤ , Audi 80 1992 ➤ , Audi A1 2011 ➤ , Audi A2 2001 ➤ , A ...
Refrigerant R134a Servicing - Edition 01.2011
4. Diagnosis and Testing 187