Air Conditioning Control

Operation
The A/C compressor, the evaporator control and the [1][2]auxiliary fan stage 1 are switched on when the air conditioning or recirculated air button is pressed.

Evaporator sensor:
The magnetic clutch of the A/C compressor is disengaged and the [1][2]auxiliary fan stage 1 switched off when the evaporator sensor reaches a temperature of < 20 C in order to prevent icing of the evaporator. At an evaporator sensor temperature of > 30 C, the control unit switches the auxiliary fan stage 1 on again and the magnetic clutch engages.

Pressure switch:
In order to improve the cooling capacity, the [1][2]auxiliary fan stage 2 is switched on when the coolant pressure increases to above 18 bar. The auxiliary fan stage 2 is switched off again when the pressure drops below 15 bar. The activation circuit of the A/C compressor clutch leads from the output of the A/C relay (working circuit) to the coolant high pressure switch (30/21 bar) and via the low pressure switch (1.5/2.6 bar) to the A/C compressor clutch. When one of the pressure switch is cut out because there is too little or too much pressure in the coolant circuit (no or too little coolant or too much coolant), the A/C compressor clutch disengages in order to prevent the compressor being damaged.

NOTE: On the M50 engine, the low pressure and high pressure switch is connected between the IHKR2/3 and the DME control unit.