High Pressure Sensor Pressure Signal
- A - Refrigerant system pressure, high pressure side in bar (absolute pressure)
- B - Signal ratio of square wave signal
- C - Characteristic curve
• The Climatronic control module (J255) A/C control head switches the compressor on at a duty cycle greater than 12% (equivalent to an absolute pressure of approx. 1.8 bar) and less than 87.5% (equivalent to an absolute pressure of approx. 32 bar) if no compressor shutoff condition is present (by activating the A/C compressor regulator valve (N280).
• The compressor is not switched on if the duty cycle is smaller than 12 % or greater than 87.5% (A/C Compressor Regulator Valve (N280) is not activated).
• The duty cycle and pressure calculated by the Climatronic control module (J255) A/C control head are indicated in the measured value block (display group "001")
• In terms of absolute pressure, 0 bar corresponds to an absolute vacuum. Normal ambient pressure equals approximately 1 bar absolute pressure. 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 Climatronic control module (J255) A/C control head transmits the request to activate the coolant fan(s) (V7) via the comfort data bus system to the engine control module. The engine control module then switches the coolant fan(s) (V7) on via the coolant fan control module (J293):
• Depending on the version of the Climatronic control module (J255) A/C control head, the coolant fan is switched on immediately in the A/C system mode when the compressor is switched on or the coolant fan is only activated when a pressure of approx. 9 bar is exceeded in the refrigerant circuit.
• The Climatronic control module (J255) A/C control head transmits the request for an increased speed of the coolant fan(s) (V7) via the comfort data bus system to the engine control module:
• 100% is currently first required at a pressure of approx. 26 bar in the refrigerant circuit.
• The signal generated from High Pressure Sensor ( G65) is also used to control the engine. The Climatronic control module (J255) A/C control head sends the information to the engine control module via the comfort data bus system (the necessary torque to drive the compressor depends on the pressure in the refrigerant circuit). Depending on the version of the engine control module, the signal is displayed in the measured value block as a duty cycle. Refer to => Vehicle Diagnosis, Testing and Information System VAS 5051 in the "guided fault finding" function.