Refrigerant Temperature Sensor G454 Function And Signal Utilization - Audi Q7 2007 Repair Manual

This pattern appears on oscilloscope screen (for example on the
Vehicle Diagnosis, Testing And Information System - VAS5051
A- ) when the following conditions are met:
– the ignition is switched on (B+ at terminal "3" and ground ter‐
minal "1" on the High Pressure Sensor - G65- present)
– Oscilloscope settings: 5 V/div. DC (5V per unit DC) 5 ms/div.
(5 milliseconds per unit)
– Measuring lead (signal wire) connected to terminal "2" on the
High Pressure Sensor - G65- .
– Measuring lead (shielding) connected to terminal "1" (ground
on the High Pressure Sensor - G65- ).
Note
To connect the High Pressure Sensor - G65- , for example,
♦
measuring leads from the Connector Test Set - VAG1594C-
may be used.
The display shows a signal that is transferred when the pres‐
♦
sure in the refrigerant circuit is approximately 7 bar, it corre‐
sponds to an approximate duty cycle of 25% (with compressor
not engaged, an ambient temperature of 30° C and properly
filled refrigerant circuit).
The impulse width -A- depends on the pressure in the refrig‐
♦
erant circuit (if pressure increases, area -A- gets wider).
The signal distance -B- is always 20 milliseconds (corre‐
♦
sponds to frequency of 50 Hertz).
The duty cycle is determined by the ratio of impulse width
♦
-A- and signal distance -B-.
3.5 Refrigerant Temperature Sensor -
G454- Function and Signal Utilization
WARNING
♦ The connection on which the Refrigerant Temperature
Sensor - G454- is installed does not possess a valve,
therefore the Refrigerant Temperature Sensor - G454-
may only be removed with a discharged refrigerant circuit.
Currently, the Climatronic Control Module - G454- does not use
the measured value from the Refrigerant Temperature Sensor -
J255- to shut off the A/C compressor. If the vehicle has a refrig‐
erant temperature sensor -G454- then the "adaptation" feature
shuts off the temperature signal evaluation. Use the Vehicle Di‐
agnostic Tester via the "Guided Fault Finding" function.
Heating, Ventilation and Air Conditioning - Edition 04.2013
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permitted unless authorised by AUDI AG. AUDI AG does not guarantee or accept any liability
with respect to the correctness of information in this document. Copyright by AUDI AG.
Audi Q7 2007 ➤
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3. Refrigerant Circuit