BMW E46 318i 2000 - Cooling fan not working - Fixed # Archived Message
Posted by Sean Connelly on June 29, 2010, 10:51 pm
Hi All,
This car's cooling fan will not operate.
Power and ground checked ok to fan assembly. Bypassing fan control unit and fan will run.
DTCs checked in engine ECU and the following permanent fault found as recorded by MTPro (via 20 pin diag connector) :-
108 - Activation, electric fan short circuit to B- /electric fan malfunction
Tried to activate fan via data link and nothing happens.
Live data checked and coolant temperature, electric fan duty cycle show valid values.
Checked signal wire from engine ECU to for continuity and open/short circuit to ground and battery supply.
Scoped signal wire and with no fan demanded the output is flat lined at 4.2V. Turn the aircon on and the fan duty cycle increases such that live data shows approx 67% and the signal line now shows a 110Hz square wave (4.2V) with a 32% duty cycle (i.e. longer off period than on period).
So fairly confident that the engine ECU is requesting the fan to operate so suspect that the fan control unit is at fault. Have read that earlier units had this unit internal to the fan and would fail but this is the later style with unit mounted to the side of the motor.
Just a little unsure of how the engine ECU is being able to flag this DTC......is it setting it because the fan control unit isn't affecting the output signal in someway? Have tried to verify the DTC through EOBD but I can't get any comms through the 16 pin connector on this vehicle despite using 3 other diagnostic tools.
Just looking for some reassurance we're on the right track before we recommend a new fan assembly as we don't believe the fan control unit will be available separately.
Thanks for looking.
Sean
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Link: http://www.maccmot.com
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- BMW E46 318i 2000 - Cooling fan not working - Fixed # - Sean Connelly June 29, 2010, 10:51 pm
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