Display Group 001

Display Group 001

A/C Compressor Regulator Valve -N280-, A/C Clutch Relay -J44- and High Pressure Sensor -G65-

Display Field 1, Part 1:

Display Field 1, Part 2:

- Depending on vehicle battery voltage a maximum current of 0.65 amps flows, when the regulator valve is fully activated (controlled and limited by A/C Control Head -E87-).

CAUTION!
The compressor performance cannot be regulated when the A/C Control Head -E87- is coded for A/C clutch -N25-. The compressor is either switched on or off (a current of only 200 milli amps flows the coil of A/C Clutch Relay -J44-). With this coding the A/C Compressor Regulator Valve -N280- is fully activated and the compressor can be damaged.

- If a malfunction has been detected on Evaporator Vent Temperature Sensor -G263-, the A/C Control Head -E87- switches to an emergency mode and the A/C Compressor Regulator Valve -N280- is activated with a pre-assigned maximum control current from -E87-. The maximum control current can be between approximately 0.3 A to 0.5 A, depending on the currently installed A/C Control Head -E87- version (however the cooling performance at lower or higher temperatures is not sufficient).

The following applies for vehicles with compressors using A/C clutch -N25- (coding of -E87-):
- The assignment of display field 1 depends on the A/C Control Head -E87- version.
- If the A/C Control Head -E87- is coded with an A/C Compressor Regulator Valve -N280-, a current of approximately 200 milli amps is displayed (current that flows through coil of A/C Clutch Relay -J44-). The compressor cannot be regulated.

Display Field 2:

Notes for display field 2:
- Display field 2 shows duty cycle for time in during which the current can actually flow.
- The A/C Control Head -E87- works with frequency of 500 Hz (500 Hertz = 600 switch impulses per seconds). The duty cycle indicates how great the activation time period is per impulse.
- The switch-on signal can be checked using with VAS 5051 using function "Test Instruments" .

The following applies for vehicles with compressors using A/C Compressor Regulator Valve -N280- (coding of -E87-):
- The duty cycle of A/C Control Head -E87- is so selected, that the specified evaporator temperature (depending on certain influences) on Evaporator Vent Temperature Sensor -G263- is attained.
- If a malfunction has been detected on Evaporator Vent Temperature Sensor -G263-, the A/C Control Head -E87- switches to an emergency mode and the A/C Compressor Regulator Valve -N280- is only activated with maximum current of 0.3 to 0.5 A (300 to 500 mA) (the duty cycle depends on the current vehicle voltage, the cooling performance of the air conditioning is therefore less and at higher temperatures the cooling is not sufficient).

The following applies for vehicles with compressors using A/C clutch -N25- (coding of -E87-):
- If the A/C Control Head -E87- has been incorrectly coded with A/C Compressor Regulator Valve -N280-, the malfunction (on vehicles with compressor using A/C clutch -N25- not installed) will be stored in the DTC memory, the compressor will be switched on anyway via the A/C Clutch Relay -J44- (a current of approximately 200 mA flows through the coil of -J44-).
- The compressor performance regulation is externally not possible, the A/C clutch -N25- can only be switched on or off by the A/C Clutch Relay -J44-.

Display Field 3, Part 1:

Display Field 3, Part 2:

- The High Pressure Sensor -G56- operates with a frequency of 50 Hz (50 Hertz = 50 activation impulse per second). The duty cycle indicates how great the activation time period is per impulse.
- The activation signal can be checked with VAS 5051 using function "Test Instruments", checking High Pressure Sensor -G65-.
- The signal that is transferred when the pressure in the refrigerant circuit is approximately 5 to 6 bar, corresponds to an approximate duty cycle of 22% (with compressor not engaged, an ambient temperature of 20 °C and properly filled refrigerant circuit)

The following applies for vehicles with compressors using A/C Compressor Regulator Valve -N280- (coding of -E87-):
- If the pressure in the refrigerant circuit or the engine coolant temperature is too high, the A/C Control Head -E87- regulates the compressor performance (to avoid sudden compressor cut- off):
- When pressure in refrigerant circuit exceeds 30 bar (absolute pressure) (the complete compressor output is only switched again after the pressure is less than 16 bar released after pressure became less than 16 bar).
- As soon as the coolant temperature reaches 115 °C (at 118 °C compressor is switched off completely).
- The signal generated by the High Pressure Sensor -G65- is also used to control the engine (the torque that is necessary to drive the compressor depends on the pressure in refrigerant circuit).
- Depending on the duty cycle, the A/C Control Head -E87- transfers a signal via the CAN-bus system to the respective Engine Control Module (ECM), the ECM switches via the Coolant FC (Fan Control) Control Module -J293- the coolant fans on.

The following applies for vehicles with compressors using A/C clutch -N25- (coding of -E87-):
- The A/C Control Head -E87- switches the compressor off when the engine coolant temperature exceeds 118 °C, the compressor is switched on again after temperature drops below 115 °C.
- The A/C Control Module -E87- switches the compressor off when the pressure in the refrigerant circuit exceeds 30 bar (absolute pressure), the compressor is switched on again after pressure drops below 16 bar.
- As soon as the pressure is exceeded (depending on duty cycle) the A/C Control Head -E87- switches the coolant fans on by activating the respective relays/control module.