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Words of wisdom on e46 (6 cylinder) cooling fan

 
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PJK



Joined: 14 Feb 2002
Posts: 1829
Location: Shingle Springs, CA

PostPosted: Mon Apr 23, 2012 4:33 pm    Post subject: Words of wisdom on e46 (6 cylinder) cooling fan Reply with quote

I'm not in the e46 club as yet. My e36 is serving me well.

I am dealing with an intermittent cooling fan issue on my daughter's e46. The complaint is that in traffic the engine overheats and the AC quits. So far what I have been able to figure out is that the electric fan quits and the smarts in the AC detects too much high side pressure and shuts down the AC. So far I have not seen it act up. The car has no belt driven fan. The electric fan is speed controlled by computer somewhere (DME or dedicated cooling system?). Hopefully a Bentley is on the way. So far what I know is that on the fan shroud is a control box. There is a three pin connector with two large (~#10) wires for power. They are always powered even with the key off. There is also one small wire which is a control signal. It is a pulse width modulated signal. At idle yesterday the period of the signal was 10 ms. The amount of time which the signal is low appears to be proportional to the desired fan speed. At idle the signal was low for ~3ms with the AC off. If I disconnect the fan for a couple of minutes letting the radiator heat upon reconnecting the fan the down time is ~6 ms and it drifts back to 3ms as the radiator cools. Turning on the AC does not immediately bump up the fan speed but as the radiator heats the low time of the signal increases with the attendant increase in fan speed.

I will have to catch this thing in the act to see if the PWM signal is present with the fan not turning to isolate the problem to the box on the fan shroud or to the source of the PWM signal. An idea where the computer is or any experience with this issue? I know that the final stage problems for the AC blower in the e46 are legendary so that makes me think the little box on the fan shroud which is comparable could be going south.

Phil
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guscavalieri



Joined: 02 Nov 2010
Posts: 2

PostPosted: Mon May 04, 2015 11:59 am    Post subject: Reply with quote

Just replace the fan assembly, the controller is right beside the fan...
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