Refrigerant Temperature Sensor -G454-
The refrigerant temperature sensor (with temperature-dependent resistance) is installed in the high pressure line near the A/C compressor, for example (only for certain vehicles that were built within a certain time frame, for example Audi Q7 from MY 2007).
In the refrigerant circuit, there is a direct correlation between temperature and pressure. Should there be too little refrigerant in the refrigerant circuit, the temperature in the refrigerant circuit increases more steadily than intended for this pressure when the A/C system is operating.
Installed on the Audi Q7 with certain engines, for example. Refer to Refrigerant Circuit (vehicle-specific repair information) and the appropriate Wiring Diagram.
The Climatronic Control Module -J255- display control head evaluates the pressure and temperature in the refrigerant circuit and switches the A/C compressor off if the temperature exceeds the value that was stored for this pressure. Refer to Refrigerant Circuit (vehicle-specific repair information) and the appropriate Vehicle Diagnostic Tester ("OBD" function or "Guided Fault Finding" for the A/C system).