Refrigerant Circuit

Evaporator Control (Compressor Control)

Evaporator control (compressor control)
Evaporator control is activated by pressing the A/C button in the operating unit. A/C standby mode is indicated by the LED in the A/C button. If controlled compressors are installed, the cutout threshold is dependent on the outside temperature and may be between 1 degree C and 3 degree C. If a standard compressor is installed, the threshold is reduced by 1 degree C at high outside temperatures (> 30 degree C). The compressor and auxiliary fan are controlled directly by the digital engine or diesel electronics (DME/DDE). Requests for A/C compressor and auxiliary fan are sent via the K-bus to the DME/DDE. The pressure sensor also monitors the refrigerant pressure and switches the A/C compressor off if the pressure is too high or too low.

Switching conditions for the magnetic clutch:
ON: A/C button ON and evaporator temperature > 4 degree C (depending on the outside temperature) and coolant temperature < 117 degree C and terminal 30 at control module > 9.7 Volt.

OFF: A/C button OFF or evaporator temperature < 3 degree C (depending on outside temperature) or blower stage 0 or coolant temperature > 120 degree C or terminal 15 OFF or terminal 30 < 9 Volt.

Switching conditions for DME AC idle boost:
When the A/C button is pressed, the heating/air conditioning system requests an idle speed boost via the K-bus in order to provide adequate cooling capacity at idle speed.

ON: A/C button ON and outside temperature > -10 degree C.

OFF: A/C button and DME_KO OFF or blower 0 and DME_KO OFF or outside temperature < -10 degree C and DME_KO OFF

DME_KO compressor activation:
The DME/DDE receives the instruction to switch on the compressor via the K-bus. Provided full load cutout is not active, the DME switches on the compressor via a relay. The load moment of the A/C compressor is derived from the pressure sensor signal and passed on to the DME/DDE via the K-bus.

Infinitely variable auxiliary fan control:
The refrigerant pressure in the air conditioning is registered by means of a pressure sensor and converted by means of a table into an auxiliary fan stage which is then sent to the DME/DDE via the K-bus/CAN bus. From this, the electronic engine control system then generates the control voltage for the infinitely variable fan motor.

IMPORTANT: New function of the ihkr46 and ihka46 as from SW: V005.0:
Vehicles concerned: E46 as from production break PU99 and parts from parts sales. The new software is backwards compatible. The control modules must be coded.

A protection function for the compressor has been integrated in the control module. The A/C LED flashes during initial operation and new coding of the control modules. Now operate the air conditioning system for 90 seconds at idle speed. The refrigerant and refrigerator oil are mixed and distributed during this 90 second period. The A/C LED then lights permanently. This procedure avoids an excessively high start-up torque and damage to the compressor.