GF07.61-P-4012MLK ME Thermal Management, Function
GF07.61-P-4012MLK ME Thermal Management, Function
- refinement package
- 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) regulates 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
- Comfort AAC control and operating unit (N22/7), air conditioning status over the interior CAN (CAN B) and engine compartment CAN (CAN C)
Thermal management function sequence
The ME-SFI [ME] control unit indirectly actuates the engine and air conditioning electric suction fan with integrated control (M4/7). The nominal fan speed is specified via a PWM signal by the ME-SFI [ME] control unit.
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 comfort AAC control and operating unit sends the air conditioning status over the interior CAN and engine compartment CAN to the ME-SFI control unit.
If the coolant temperature is too high, a warning message is shown on the multifunction display at the top (A1p13) of the instrument cluster (A1). To do this, the ME-SFI control unit sends the corresponding CAN signal over the engine compartment CAN 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.
