Audi A2 2001 - Page 190

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Note
♦ If the function of the air conditioning system is not OK when
the test is repeated, replace expansion valve and receiver.
♦ With this malfunction, evaporator may ice up although quantity
of refrigerant in circuit is OK.
♦ If expansion valve is malfunctioning (permanently closed or
does not open sufficiently), A/C compressor regulator valve -
N280- is actuated to maximum output and low pressure drops
to value in graph or below (compressor draws off refrigerant
from low-pressure side). As refrigerant cannot flow via expan‐
sion valve, cooling output is not attained, high pressure may
also not increase or only increase slightly due to the absence
of energy. Check using Vehicle Diagnosis, Testing & Info.
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).
♦ If there is too much refrigerant oil in the circuit, the compressor
must be drained and the accumulator must be replaced. After
cleaning the refrigerant circuit (flushing with refrigerant R134a,
refer to
⇒ “1.4.13 Refrigerant Circuit Flushing With Refrigerant
R134a“, page 32 or blowing through using compressed air and
nitrogen, refer to
⇒ “1.4.12 Refrigerant Circuit Flushing With Compressed Air
and Nitrogen “, page 29 ) the correct quantity of refrigerant oil
is filled into the circuit, refer to
⇒ “3.4 Refrigerant Oil Capacities“, page 119 .
Possible deviation from speci‐
fication
Possible cause of fault Corrective action
• High and low pressure nor‐
mal at first After some time,
• high pressure increases
above specification
• Low pressure quickly drops
to value in graph or below,
• Required cooling output is
no longer attained.
♦ Actuation of A/C compressor regulator
valve -N280- malfunctioning
♦ Moisture in refrigerant circuit
– 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 ).
• High and low pressure nor‐
mal at first
• After lengthy driving time,
low pressure drops exces‐
sively (evaporator ices up)
– Replace receiver with dryer.
– Evacuate refrigerant circuit
for at least 3 hours.
– 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
186 Rep. Gr.00 - General, Technical Data