A/C Compressor Control

A/C COMPRESSOR CONTROL







Activation of the compressor clutch is an output control function of the IHKA module. As with the E38 IHKA, activation is carried out directly through a final stage in the module (no relay required).

The signals KO and AC have been combined into one signal providing multiple data through a stepped increase in signal duty cycle.

Signal KO: - 15% Duty Cycle: IHKA is OFF
- 30% Duty Cycle: IHKA is switched ON (Standby).
- 45% Duty Cycle: Snowflake button is pressed, the IHKA signals the engine control module to raise the idle speed in preparation of the compressor being switched on. This takes place before the IHKA energizes the compressor.

Signal Korel:
The engine control module signals the IHKA (Signal KOREL) when the idle increase has taken place and the IHKA will then activate the compressor clutch, as long as all other compressor requirements are satisfied. Compressor cut off conditions include:

- Evaporator temperature below 2°C
- Coolant temperature > 117°C - causes the compressor to run in a pulsed operation.
- Coolant temperature > 120°C - the compressor clutch is deactivated until the temperature drops below 117°C.
- Full acceleration at low speeds - below 10 mph with a full throttle input will cause the compressor to shut off for 10 seconds.