Rear A/C System, Testing Cooling Performance - Audi Q7 2007 Repair Manual

Audi Q7 2007 ➤
Heating, Ventilation and Air Conditioning - Edition 04.2013
13.3 Rear A/C System, Testing Cooling Per‐
formance
⇒ "13.3.1 Test Prerequisites", page 228
⇒ "13.3.2 Rear Cooling Output, Checking", page 229
13.3.1 Test Prerequisites
Note
If there is a complaint at only the evaporator in rear A/C unit
♦
on vehicles with two evaporators, first perform cooling per‐
formance testing at front A/C system. Refer to
⇒ "13.2 Front A/C System, Testing Cooling Performance",
page 215 . If cooling performance at front is OK, check cooling
performance at rear A/C system. If, during cooling perform‐
ance testing on rear A/C system, it is detected that perform‐
ance is not sufficient and then no cause for the complaint can
be found, check line connection between evaporator in ques‐
tion and exit of line connection at distribution point of refriger‐
ant lines in left front wheel housing (for example, for
constriction). If the fault cannot be found, bring the vehicle to
a workshop that has the necessary tools and in which the work
can be performed accordingly by qualified personnel (there is
a problem in the refrigerant circuit). Refer to ⇒ Refrigerant
R134a Servicing; Rep. Gr. 87 ; A/C System General Informa‐
tion (A/C System with Refrigerant R134a; A/C System, Gen‐
eral Information).
There is no sensor that measures air temperature downstream
♦
of evaporator installed in the rear A/C unit, compressor per‐
formance control is performed therefore only via the measured
value of the Evaporator Vent Temperature Sensor - G263- ,
which is installed in the front A/C unit. Under certain unfavor‐
able conditions, it may occur therefore because of this that the
temperature set on the rear A/C unit is not attained during
normal regulated operation even though the A/C system is OK.
Also it may occur that, for example, on an A/C system on which
the specified outflow temperature has already been attained
in the front A/C unit and maximum cooling output is requested
at rear A/C system, the rear outflow temperature is a few de‐
grees° C higher than when a high cooling output is requested
at front A/C system (if necessary increase front cooling output
via setting at front).
♦ Cooling performance of front A/C system was checked and is
OK. Refer to
⇒ "13.2 Front A/C System, Testing Cooling Performance",
page 215 .
♦ Test requirements for testing front cooling performance are
met. Refer to ⇒ "13.2.1 Test Requirements:", page 215
♦ The air intake for the Rear Fresh Air Blower - V80- via the air
intake grille installed in left luggage compartment lining is not
obstructed by objects. Refer to
⇒ "12.4 Air Duct in Rear A/C Unit", page 211
228
Rep. Gr.87 - Air Conditioning
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