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Old 11-15-2016, 09:11 AM   #1
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BMW E46 318i SE Manual "Yet another" Overheating in traffic

OK so I have this posted this on another BMW forum too but it seems that I've exhausted knowledge there

I've had the car about 3 weeks now and done around 1500miles, so far so good apart from one thing... In traffic after a run she over heats.

Heres what I've got:
Cooling fan not working, INPA gave "279D CDKMLE - Control engine fan" which I Googl'd as "279D Electric Fan Output Stage"
Fan replaced, still same error
Power at the pins and fuse OK. No voltage on PWM.
Fan doesn't engage with air con on, no pressure in A/C system.
Fan doesn't come on when sensor unplugged from bottom radiator hose.
I'm manual gears so no pusher/mechanical fan.

What is the box on top of the radiator fan housing? Also where does the third pulse control wire go?
Could it possible be the DME? I know I will need to replace the wire/check the DME PWM at the source before I rule it out but its something I have to take into consideration?

I have a new radiator, top and bottom hoses, new coolant temp sensor (bottom hose one, I am led to believe there is another also, does this need changing? I can get the temperature reported fine), water pump, thermostat.

Any assistance welcomed!
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Old 11-16-2016, 08:24 AM   #2
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The box on the top of the radiator is the AUC: it senses for polluted air and sends the climate control into the recirculate mode IF the climate control is set to "auto recirc." Dumb in my opinion! Ignore it as it has no bearing on your problem.

The electric fan has power at all times. Why? The engine computer (ECU) can enable the fan if the engine temp is above a specific temp and the engine is off. Smart Germans.

As yo noted, there's no power on the third, thin wire. This is wire used by the ECU to control the fan. The signal type is pulse wave modulation (PWM). You won't likely see voltage on that wire unless you use an oscilloscope.

Is the new fan made by a reputable manufacturer? Or, is it from eBay?

Here's a great document of troubleshooting the fan:
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Old 11-16-2016, 08:33 AM   #3
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Thanks for the reply, that 48 page document will make for some light reading
The fan is genuine BMW and cost 1/3rd that of the car. I was tempted with an eBay fan but was put off by the fact that the modules seem to be made of turd anyway.
After swapping it I still have the same fault code & I can't activate it with INPA.
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