ME thermal management, function - GF07.61-P-4012MOS

ENGINE 275.953 in MODEL 216.376, 221.176 as of Model Year 09 /AEJ 08

ENGINE 275.982 in MODEL 216.379, 221.179 as of Model Year 09 /AEJ 08

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.

Electrical function schematic for thermal management	Model 216	PE07.61-P-2791-97CAA
Electrical function schematic for thermal management	Model 221	PE07.61-P-2791-97SAA
ME-SFI [ME] control unit, component description	N3/10	GF07.61-P-6000MOS