Audi TT - Page 101

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Note
♦ The cooling output cannot be checked when the high pressure
sensor is removed. The Climatronic control module -J255- will
not switch on the A/C compressor. Refer to Vehicle diagnosis,
testing and information system -VAS5051B- under "Guided
Fault Finding".
♦ After switching off the A/C compressor in this vehicle, it may
take a relatively long time for the pressure on the high pressure
side to decrease. This is because the expansion valve is cold
and the pressure on the low pressure side increases quickly
after shutting the compressor off, then the expansion valve
closes and the refrigerant flows slowly to the low pressure
side.
♦ Depending on the version of the high pressure sensor, an in‐
sufficient measuring value for the pressure in the refrigerant
system will be sent by the high pressure sensor at low outside
temperatures (lower than 5 °C) (even though the A/C system
is OK and the refrigerant circuit is properly filled). At lower out‐
side temperatures (ambient temperature lower than 5 °C), A/
C System control heads—the Climatronic control module with
part number “8J0 820 043“ through to index “AJ“—might there‐
fore make an incorrect DTC memory entry (DTC memory
entry: high pressure sensor “, and fall below the lower thresh‐
old“). If the fault is displayed as a sporadic fault at an outside
temperature greater than 5 °C, calculated by the A/C system,
and if the A/C function is OK, then clear the DTC memory (no
additional steps are necessary). This error does not occur with
—the Climatronic control module, part number “8J0 820 043“
beginning with index “AK“.
Test Sequence
The High Pressure Sensor -G65- -item B- is at the right on the
bottom of the condenser.
– Disconnect electrical connector -A-.
Routing 3-pin connector on High Pressure Sensor -G65-
1 - Ground
2 - Signal output - Square wave signal to Climatronic control
module -J255-
3 - Terminal 75 (positive)
Note
♦ With electrical connector -A- disconnected, the A/C compres‐
sor is not switched on.
♦ The high pressure sensor -G65- -B- is an electronic control
module, which creates a square wave signal, the duty cycle
ratio changes with pressure in the refrigerant circuit. Refer to
⇒ “2.15 High Pressure Sensor G65 Signal“, page 72 .
♦ Pressure signal from the high pressure sensor, refer to
⇒ “2.15 High Pressure Sensor G65 Signal“, page 72 .
Audi TT 2007 ➤
Heating, Ventilation and Air Conditioning - Edition 01.2011
4. Diagnosis and Testing 97