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– Bring vehicle to a work‐
shop that has the neces‐
sary tools and in which
the work can be per‐
formed accordingly by
qualified personnel. Re‐
fer to⇒ Refrigerant
R134a Servicing; Rep.
Gr. 00 ; General Infor‐
mation . Bring the prob‐
lems determined to the
attention of the work‐
shop.
– Check the radiator fan actuation in “output diagnostic test mode“. Refer to -
VAS5051B- in "Guided Fault Finding."
– Repair the radiator fan activation.
– Repeat cooling performance test. Refer to
⇒ “4.2 A/C Unit, Checking Cooling Output“, page 79 .
Note
♦
The pressure in the refrigerant circuit depends on several fac‐
tors. However, in general, the pressure should not exceed 20
bar at an ambient temperature of 20 to 25 °C. Pressures up to
31 bar may occur due to extremely high performance under
severe conditions (such as in southern countries with a hot
climate, “stop and go“ traffic and high humidity).
♦
At ambient temperatures below 25 °C, pressure in refrigerant
circuit does not normally exceed 16 bar (coolant fans run and
cool condenser).
♦
The Climatronic control module -J255- calculates the refriger‐
ant circuit pressure using the duty cycle signal from the high
pressure sensor -G65- (display in the measured values block).
At a duty cycle less than 10% (corresponds to approximately
1.2 bar absolute pressure) and greater than 78% (corresponds
to approximately 32 bar absolute pressure), Climatronic con‐
trol module does not switch on the compressor ( A/C Com‐
pressor Regulator Valve -N280- is not activated). The A/C
compressor is only switched on again after duty cycle has be‐
come greater than 12% (corresponds to 1.8 bar absolute
pressure) or less than 74% (corresponds to 29 bar absolute
pressure).
♦
If the pressure in the refrigerant circuit or the engine coolant
temperature is too high, Climatronic control module regulates
the A/C compressor performance (to avoid sudden A/C com‐
pressor cut-off). As soon as pressure in refrigerant circuit
exceeds 30 bar (absolute pressure), full compressor perform‐
ance is only enabled again after pressure has become less
than 27 bar, or coolant temperature exceeds 115 ℃ (it is
switched off completely at 118 ℃ ).
♦
If the pressure in the refrigerant circuit was greater than 32 bar
(duty cycle greater than 78%) the A/C compressor is switched
on again by the Climatronic control module, if pressure drops
below 29 bar (duty cycle is less than 74%).
♦
Additional information on pressure in the refrigerant circuit can
be found in
⇒ “4.8 High Pressure Sensor G65 , Checking Pressure Sig‐
nal“, page 96 and -VAS5051B- in "Guided Fault Finding."
Audi TT 2007 ➤
Heating, Ventilation and Air Conditioning - Edition 01.2011
4. Diagnosis and Testing 87
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