AUX fan woes

[oldskewel]

I just started troubleshooting a similar sounding problem on my 2001 3.0i. I don't want to confuse things in this thread, so first a question - how relevant are things on the OP's 2006 3.0d to my 2001 3.0i?

My symptoms are almost exactly the same as the OP. Spent some time yesterday troubleshooting things for the first time.

[upallnight]

AC principles are the same no matter if it is a gasoline X5 or a diesel X5.

[oldskewel]

@UPGrayd, from electrical measurements, taking things apart, etc., and with very similar symptoms to yours, I have almost certainly concluded that my fan motor is bad.

The key thing that is confusing your and my situations is that even with a failed motor (failed in that it will not spin when properly commanded to spin by the ECU), it will still bump a little sometimes upon startup.

My measurements and Foxwell active testing all seem to confirm that everything is working other than that the fan actually spins. I don't get any codes, warning messages, lights, etc. It just does not spin.

Also surprising is that even after failing to spin at the startup, it will continue to be commanded correctly during further operation. Why do the bump-and-spindown test, get a failure result, and then (1) don't report or silently log the failure, and (2) continue to command the fan to spin as if it had passed? But that's what it appears to do.

I can't find any info on the diesels, but I did confirm that ALL non-diesel E53s now use the same fan. 3.0i, all the way up to 4.8is.

From realoem:
https://www.realoem.com/bmw/enUS/sho...diagId=64_1087

BMW PN for the full assembly: 64546921381, which supersedes:
64546921940 (11/12/2001 — 08/16/2004)
64546919051 (06/01/2001 — 10/31/2001)
64506908124 (12/01/1999 — 06/20/2001)
64548380573 (10/01/1999 — 03/17/2000)
There was a recall back in the day, and the ...381 was installed when doing the recall service.

I think I fit the category of the aux fan being non-essential, but plan to replace it when convenient.

[andrewwynn]

just to add confusion I just did two starts in a row and nothing; no spin at all and my fan works fine. It was not a coldstart so maybe just on a coldstart it does the fan bump.

[oldskewel]

Originally Posted by andrewwynn

just to add confusion I just did two starts in a row and nothing; no spin at all and my fan works fine. It was not a coldstart so maybe just on a coldstart it does the fan bump.

Interesting result. Very helpful. Thanks. Not completely surprised. This subsystem seems more complex than people give it credit for.

From reading many sources on the interwebs, I'm seeing that there are some things in the way they control this that can lead to oversimplification and confusing reports / conclusions. E.g., as you are noticing, maybe the test spin on startup is temperature dependent somehow ???

If you are feeling adventurous and curious, here are a couple of specific observations I made about my car, that you might like to duplicate. I believe my fan motor has failed, and is the only failure. I measure the ECU command signal on the thin wire, just using my True RMS meter, measuring DC voltage. It seems good enough for debugging, giving me an integrated average signal that refelects the duty cycle of the square wave the ECU is sending to the controller.

Engine idling, AC off, car and ambient fairly cold (closer to 70F than 100F).

(1) Turn AC on. The fan will immediately spin, but not too fast, gradually increasing a little. Mine sat like that for a minute or two before I ended the test. My fan was not moving at all (maybe a bump on the initial AC on), but so my result is based on watching the control voltage drop (lower duty cycle means faster spin). I expect that as the temperature of everything increased, the fan would spin faster.

(2) AC off. Disconnect the connector to the temp sensor on the lower radiator hose. Put a 100 Ohm resistor in there across the connector. According to the Foxwell live data, this resistance value makes the ECU think the temp there is 241F (hot). The fan control voltage values indicate that over a period of about 30 seconds, the fan speed ramps up to almost full speed. Interesting how it was an immediate initial response, but then a gradual build up in speed. So the ECU is making full use of the variable speed control, and fairly complex logic in deciding how to spin the fan. Also, there were no effects or notifications anywhere on the instrument panel (mine is high cluster) about this high temp.

(3) Foxwell active test makes it run at the highest speed (lowest control voltage as I measured = 1.6V [average voltage on a pulse width modulated duty cycle of a ~14V square wave]), instantly jumping to that and holding steady for 20 seconds. This test does not require the engine to be running.

[UPGrayd]

Originally Posted by upallnight

A motor has to spin fast enough to create a voltage so the motor must spin for quite some tme and then free spin to create the electrical signal. Spinning only a 1/2 turn will not create an electtrical signal that will be recognize by the DME.

If he could unclip the front grille in front of the fan I would do that and see if the fan spin freely by hand. Could be the fan bearings are shot.

Sorry I havnt been back to check on the thread in a few days. I have had a bit going on. The first thing I did when I noticed the fan not behaving as it should was pull the cover off and check it spins freely, It does spin freely and there is no play in the bearing.

I have ordered the cable I need to test it though. I guess I just have to wait until that arrives. While I was hoping to not have to buy one, I plan on keeping the X for quite a while, so either way its an investment.

[andrewwynn]

You need BMW level scan tool, I'm assuming you mean a cable to hook up BMW scan software, that will help you immensely.

[UPGrayd]

Originally Posted by andrewwynn

You need BMW level scan tool, I'm assuming you mean a cable to hook up BMW scan software, that will help you immensely.

Yes, the appropriate cable to use with INPA

[andrewwynn]

Make sure the appropriate pins are jumpered to access all modules.


Sent from my iPhone using Tapatalk Pro

[UPGrayd]

I will, as that was an issue I came across when trying to figure out a 4x4 warning using a friends cable a while back...I couldnt exactly pull his apart and start soldering pins together though....The one I've ordered apparently has a switch on it for that though.