Audi Q7 2007 Repair Manual page 232

Audi Q7 2007 ➤
Heating, Ventilation and Air Conditioning - Edition 04.2013
– Bring the vehicle to a
workshop that has the
necessary tools and in
which the work can be
performed accordingly
by qualified personnel
(notify the workshop
about the malfunction).
Refer to ⇒ Refrigerant
R134a Servicing; Rep.
Gr. 87 ; A/C System
General Information
(Refrigerant R134a,
Servicing; A/C System,
General Information).
Note
Pressure in refrigerant circuit is governed by various factors of
♦
influence. However, at an ambient temperature between
20-25° C (68-77° F) the pressure should not exceed more than
20 bar (290 psi). Due to high coolant performance, pressures
up to 31 bar (450 psi) may occur under extreme operating
conditions (for example, in southern countries with high am‐
bient temperatures, "stop and go" traffic and high humidity).
The pressure in the refrigerant system does not increase
♦
above 16 bar (232 psi) at ambient temperatures lower than 25°
C (77° F) (the Coolant Fan - V7- runs and cools the condens‐
er).
The Climatronic Control Module - G65- front A/C control head
♦
calculates the pressure in the refrigerant circuit via the duty
cycle (signal from the High Pressure Sensor - J255- ).
At a duty cycle less than 12.5% (corresponds approximately
♦
1.8 bar (26 psi) absolute pressure) and greater than 87.5%
(corresponds approximately 32 bar (464 psi) absolute pres‐
sure), the Climatronic Control Module - J255- front A/C control
head does not switch on the compressor ( A/C Compressor
Regulator Valve - N280- is not activated). The compressor is
only switched on again after duty cycle has become greater
than 12.5% (corresponds to 1.8 bar (26 psi) absolute pres‐
sure) or less than 48% (corresponds to 16 bar (232 psi)
absolute pressure). Use the Vehicle Diagnostic Tester via the
"Guided Fault Finding" function.
If the pressure in the refrigerant circuit or the engine coolant
♦
temperature is too high, the Climatronic Control Module -
J255- front A/C control head regulates the compressor per‐
formance (to avoid sudden compressor cut-off). As soon as
pressure in refrigerant circuit exceeds 30 bar (435 psi) (abso‐
lute pressure), full compressor performance is only enabled
again after pressure has become less than 27 bar (392 psi),
or coolant temperature exceeds 115° C (239° F) (it is switched
off completely at 118° C (244° F)).
If the pressure in the refrigerant circuit was greater than 32 bar
♦
(464 psi) (duty cycle greater than 87.5%) the compressor is
switched on again by the Climatronic Control Module - J255-
front A/C control head, if the pressure drops below 29 bar (420
psi) (duty cycle is less than 84%).
For additional information regarding pressure in the coolant
♦
circuit, Use the Vehicle Diagnostic Tester via the "Guided Fault
Finding" function.
226
Rep. Gr.87 - Air Conditioning
– Check the activation of the Coolant Fan - V7- , for example in function "output
Diagnostic Test Mode (DTM)". Use the Vehicle Diagnostic Tester via the
"Guided Fault Finding" function.
– Repair activation of Coolant Fan - V7- .
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with respect to the correctness of information in this document. Copyright by AUDI AG.