Cooling System: Notes

In the E92 M3, an electric fan is installed (as in the E70), which initially reaches a maximum output of 850 Watts. The fan is activated by the MSS60 via a pulse width-modulated signal (PWM signal) with a frequency of 100-300 Hz for fan operation, wake-up function, and interface diagnosis function.

A frequency of 10 Hz is used for overrun requests.

The signal voltage is approximately the same as the on-board supply voltage. The following cycle ratio specifications (in %) refer to the "low" proportion of the signal period.

The cooling fan power supply is produced using a 100 A high-current circuit breaker in the luggage compartment distributor and a high-voltage relay near the front passenger footwell. The relay is control by terminal 30g (CAS).

The performance of the cooling fan depends on the coolant temperature, the IHKA request, the intake air temperature, the calculated exhaust gas temperature downstream from the catalytic converter, and the request by the generator (overheating protection).

The control valve in the air conditioning compressor and the coolant pressure sensor are electrically connected to the junction box (JB). The IHKA/IHKR can use the K-CAN connection to evaluate the pressure and send the appropriate control requests for the control valve in the air conditioning compressor to the JB. A resulting load torque for the torque correction and an electric fan speed request are also sent to the MSS60 via the K-CAN.

The junction box only activates the control valve in the air conditioning compressor following release by the MSS60. The MSS60 adapts the idle speed control accordingly and activates the electric fan.

The switching state of the coolant level switch is also transmitted to the junction box and evaluated by the instrument cluster via the K-CAN connection. If there is insufficient coolant, a corresponding warning is sent to the driver.