GF07.61-P-4012MOS ME Thermal Management, Function

GF07.61-P-4012MOS ME Thermal Management, Function
- as of model year 09


Function requirements for thermal management, general points
^ Circuit 87M ON (engine control ON)
^ Engine running

Thermal management, general points
The thermal management function of the ME-SFI control unit (N3/10) is used to regulate the engine coolant temperature by controlling the fan speed.

The fan and the fan speed are controlled according to the following sensors and signals:
- Coolant temperature sensor (B11/4)
- Oil sensor (oil level, temperature and grade) (B40), engine oil temperature
- AAC control unit (N22/1), air conditioning status over the interior CAN (CAN B) and chassis CAN (CAN E)

Thermal management function sequence
The ME-SFI control unit actuates the engine and air conditioning electric suction fan with integrated control (M4/7). The specified fan speed is set by the ME-SFI control unit with a pulse width modulated signal (PWM signal).
The duty cycle of the PWM signal is 10 to 90%.

Meaning:
10% Fan motor "OFF"
20% Fan motor "ON", minimal rpm
90% Fan motor "ON", maximum rpm

If actuation is faulty, the air fan rotates at the maximum rotational speed (fan emergency mode).

The AAC control unit sends the air conditioning status over the interior CAN and chassis CAN to the ME-SFI control unit.

If coolant temperature is too high, a warning message is shown on the multifunction display (A1p13) of the instrument cluster (A1). To do this, the ME-SFI control unit sends the corresponding signal over the chassis CAN and central CAN (CAN F) to the instrument cluster.

Delayed fan switch off
After "ignition OFF", the fan motor continues to run for up to 5 min. if the coolant temperature or engine oil temperature is above the specified maximum value.
The PWM signal duty cycle is 40 % maximum while the delayed fan switch-off is active.
If the battery voltage is dropping too much, the delayed fan switch-off is stopped.