GF07.61-P-4012MFF | ME thermal management, function | 22.2.08 |
ENGINE 271.946 in MODEL 203.746 as of Model Year 09 / AEJ 08 model refinement package
ENGINE 271.957 in MODEL 203.741 as of Model Year 09 / AEJ 08 model refinement package
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 fan speed are controlled according to the following sensor and signal:
- Coolant temperature sensor (B11/4)
- Comfort AAC control and operating unit (N22/7), air conditioning status over the interior CAN (CAN B) and engine compartment CAN (CAN C)
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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).
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The comfort AAC control and operating unit sends the automatic 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 displayed in the multifunction display (A1p13) in the instrument cluster (A1). To do this the ME-SFI [ME] control unit sends an appropriate signal via the engine compartment CAN to the instrument cluster.
Delayed fan switch off
With "ignition OFF", the fan motor runs on for up to 5 min if the coolant temperature or engine oil temperature (calculated from the temperature model) exceed the specified maximum values.
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.
Referenced documents
- gf0704p6040mff Coolant temperature sensor, component description
- gf0761p6000mff ME-SFI [ME] control unit, component description
- pe0761p279197fa Electrical function schematic for thermal management