High Pressure Sensor Pressure Signal
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) front A/C control head switches the compressor on by actuating the A/C Compressor Regulator Valve (N280) as soon as no compressor shut-off condition is present:
• The signal generated from High Pressure Sensor (G65) is also used to control the engine. The Climatronic Control Module (J255) front 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 engine control module version, the signal in the measured value block is displayed as a duty cycle Vehicle diagnosis, testing and information system VAS 5051 in the "Guided Fault Finding" function.
• The pressure in the refrigerant circuit is OK the Climatronic Control Module (J255) front A/C control head does not detect a compressor shut-off condition
- If duty cycle is greater than 12 % corresponding to approximately 1.8 bar absolute and less than 87.5% corresponding to approximately 32 bar absolute
• 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) front A/C control head is displayed in the measured value block Vehicle diagnosis, testing and information system VAS 5051 in the "Guided Fault Finding" function.
• 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) front A/C control head transmits the request to switch the coolant fans on to the engine control module via the Comfort data bus. The ECM switches the coolant fans on via the coolant fan control module.
- As soon as compressor is switched on, irrespective of pressure in refrigerant circuit
- The Climatronic Control Module (J255) front A/C control head transmits the request for increased coolant speed via the Comfort data bus to the engine control module with the compressor activated, depending on the pressure calculated in the refrigerant circuit. The fan speed determined by front A/C control head Climatronic Control Module (J255) is displayed in the measuring value block Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding" function.
This pattern appears on oscilloscope screen on Diagnostic Operation System (VAS 5051 A)) when the following conditions are met.
- Ignition switched on B+ at terminal "3" and Ground (GND) terminal "1" on High Pressure Sensor (G65) present
- Oscilloscope settings: 5V / Div. = 5V per unit DC voltage 5 ms / Div. (5 milliseconds per unit)
- Measuring lead signal wire connected to terminal "2" on High Pressure Sensor (G65).
- Measuring lead shielding connected to terminal "1" (Ground -GND- on High Pressure Sensor (G65)).
• To connect High Pressure Sensor (G65), measuring leads from Connector Test Kit (V.A.G 1594 C) may be used.
• The display shows a signal that is transferred when the pressure in the refrigerant circuit is approximately 7 bar, it corresponds 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 refrigerant circuit (if pressure increases, area - A - gets wider.
• The signal distance - B - is always 20 milliseconds corresponds to frequency of 50 Hertz.
• The duty cycle is determined by the ratio of impulse width - A - and signal distance - B -.