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Home >> Audi >> 2016 >> S5 Prestige, 2D Convertible >> Repair and Diagnosis >> External Pages >> Different car >> Section 1499 (Heating & Air Conditioning (On Board Diagnostic)) >> 01 On Board Diagnostic (OBD) >> Automatic Climate Control System, electrical testing >> Test steps "5" to "9" >> Pressure signal from High Pressure Sensor G65

Pressure signal from High Pressure Sensor G65

WARNING: This page is about a different car, the 2008 Audi S4, 2008 Audi RS 4, and 2008 Audi A4. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Pressure Signal From High Pressure Sensor G65
GW00021279Courtesy of VOLKSWAGEN UNITED STATES, INC.

- A  - Pressure on high-pressure end of refrigerant circuit in bar (absolute)

- B  - Ratio of square-wave signal

- C  - Characteristic curve

NOTE:
  • The operating and display module, Climatronic Control Module J255 switches on the compressor (by way of activation of the A/C Compressor Regulator Valve N280) in the case of a ratio of greater than 12 % (corresponding to approx. 1.8 bar absolute pressure) and less than 87.5% (corresponding to approx. 32 bar absolute pressure) if there is no compressor shutoff condition.
  • If the signal ratio is less than 12 % or greater than 87.5%, the compressor does not switch on (the A/C Compressor Regulator Valve N280 is not activated).
  • The signal ratio and the pressure calculated by the operating and display module, Climatronic Control Module J255 are displayed in the measuring value block → Read Measuring Value Block (function 08)  (display group "001").
    • Fig 2: Pressure Signal From High Pressure Sensor G65
    GW00021279Courtesy of VOLKSWAGEN UNITED STATES, INC.
  • At absolute pressure, 0 bar corresponds to an absolute vacuum. Normal ambient pressure thus corresponds to roughly 1 bar absolute. On the scales of most pressure gauges, 0 bar corresponds to an absolute pressure of one bar (can be seen from -1 mark below 0).
  • The operating and display module, Climatronic Control Module J255 transmits the request for activation of the Coolant Fan V7 via the CAN-Bus comfort system to the engine control module, which then causes the Coolant Fan Control (FC)Control Module J293 to switch on the Coolant Fan V7 :
  • - As soon as the compressor is switched on irrespective of the pressure in the refrigerant circuit.
  • The operating and display module, Climatronic Control Module J255 transmits the request for increased Coolant Fan V7 speed via the CAN-Bus comfort system to the engine control module:
  • 100% is currently only requested at a pressure of approx. 26 bar in the refrigerant circuit.
  • The signal generated by the High Pressure Sensor G65 is also used for engine control. The operating and display module, Climatronic Control Module J255 transmits the information via the CAN-Bus comfort system to the engine control module (torque required for driving compressor is governed by pressure in refrigerant circuit). Depending on the version of the engine control module, the signal is displayed as a ratio in the measuring value block "Guided Fault-Finding" Vehicle Diagnosis, Testing Info. System VAS5051B or Vehicle Diagnosis Service Syst. VAS5052
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