Engine Cooling problem
2001 BMW 330 6 cyl Two Wheel Drive Manual 67000 miles
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I had a expansion tank burst on me recently. I do not know if the fan was related to that problem or not. The temp gauge never went over half when problem occured. However after putting in new tank I realized that the radiator fan is not coming on. I ran the car to the point of almost overheat to make sure that the fan wouldn't kick on at any point. The fan does however kick like it is trying to start about every minute or so while the car is running. It does not make a full rotation tho to give idea how little is moving. So here is my questions.

If the fan is bad, then far as I know this should put up a (DTC) and the engine light does not come up on dash. (light has been tested to make sure is good)
How can that be ? I even unplugged fan completely from the car and still didn't make light come on.

In trying to test the fan I noticed there are 3 wires. One hot wire, one ground, and a third. What is the 3rd wire for ? Could it be related ?

Any information would be very appreciated.

Thanks,
Jamie

Use a volt meter or test light to test the connector, if power gets to the fan, and it wont run, the fan is no good...does it come on with the a/c? It should start as soon as the ac is turned on...If the fan is bad, it might not turn on the MIL...if one of the sensors that controls it were bad, it would...

I have used volt meter on everything could think of. There is power going to that fan all the time... with the car on or off. I found that a bit odd. That is why I am curious do you know what the 3rd wire on that fan might be ??? The fan is consistent.. like I said a/c or not It kicks about every 1 min. making a 1/4 of a rotation. If the fan was bad would it even do that much ??? Also added information .. I tested resistance on fan circut and there is not a open circut, which I know is open alot of times when things like this go bad.

Thanks again,
Jamie

The three wires are power from 50 amp fuse, ground and control from the ECM, no testing info provided by BMW...Have you tried running wires from the batteyr to the fan to see if it will work? Seems only three things can go wrong...the fan, the sensor, or the control unit, maybe a bad ground....

The problem is in the final stage and that is what the third smaller wire is for as BMW sends digital logic on that bus and over that wire to the "controller" or as we say, final stage. Now having said that, the IHKA system is readable for faults and will tell you if something is wrong. All it takes to read out this info is a GT-1 from BMW or Autologic or some other scanner that can see the systems and read the faults out. Your description sounds like it has a faulty final stage and it comes complete with the fan unit. 64-54-6-922-554 is the part# and will probably supersede.

I have tried hooking up a battery direct to the fan to see if could get anything out of it. The fan does not move with a fresh car battery hooked up to it. Just wanted to be sure before spending the $400 on a new fan that there was no other possabilities of something else causing this problem. I appreciate both of you trying to help with the matter. Never seen a fan for cooling so complex as the one for this car. But I guess that's what I should expect with a bmw. Will shop around for new fan and thankyou for part number as make it easier.

Thanks,
Jamie

Well...it is after all the Ultimate driving machine! But like the Doc said, you could eliminate the guess work by scanning for codes!

A failed final stage can be tough to diagnose. Shop the price online.