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Discussion Starter #1
My 129K miles 2003 325iT wagon has this weird noise which I never noticed with my 2000 323iT: after shut off the engine there was a humming noise -- sounds like a small motor or fan running -- behind the HVAC control panel, continued for more than 5 to 10 minutes (I didn't time it). Is this normal? Is it the DME cooling fan (but why I didn't hear the noise with engine idling).

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My 129K miles 2003 325iT wagon has this weird noise which I never noticed with my 2000 323iT: after shut off the engine there was a humming noise -- sounds like a small motor or fan running -- behind the HVAC control panel, continued for more than 5 to 10 minutes (I didn't time it). Is this normal? Is it the DME cooling fan (but why I didn't hear the noise with engine idling).

Thanks.
It's probably the blower motor. Should run for a couple of minutes after you switch the ignition off and then go off. That's normal. It can be a problem if the final stage resistor (FSR) goes faulty and the motor keeps running. It can drain your battery. Just lock your car up. Go back after a half hour and if it's still running you need to replace the FSR.
 

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There is a small fan at the back of the hvac control panel. It draws air in through the little grill on the front for the interior temp sensor. It runs after the car is shut off until it goes to sleep (16 min). If yours is noisy, it probably needs to be cleaned out. Remove the control panel and blow it out with compressed air from the front and back.

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Discussion Starter #5
Not the bad FSR and blower fan running, as I had turned off the blower while driving and so no reason for it to run after turned off the key. But what do I know about this new to me car.

I tested again: turned on the key but not run the engine, then turned off key and the noise appeared. It only turned off by itself after more than 10 minutes and the thing was pulling about 0.8A at 14v when running (charger connected). I will start pull out fuses and see what the heck is it.
 

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BMW 320i 2002 e46 5spd manual RHD
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Mine did exactly the same, its the fan in the back, all i did was remove the hvac, stripped it, took the fan out, cleaned it all with compressed air, then put some bearing grease on the shaft of the blower, stick it back in, spin it a couple times, add little more, clean any access, close everything up, its been 3K km with no noise from it, (and yes i did make sure it still works)
 

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Discussion Starter #7
Mine did exactly the same, its the fan in the back, all i did was remove the hvac, stripped it, took the fan out, cleaned it all with compressed air, then put some bearing grease on the shaft of the blower, stick it back in, spin it a couple times, add little more, clean any access, close everything up, its been 3K km with no noise from it, (and yes i did make sure it still works)
So the main blower fan continued to spin after engine was turned off? If I understand you correctly, that the fan continued running for 10 more minutes is normal, and the fact that you took it out and cleaned and greased the fan bearings made it quiet no more noise but it still continued running after engine off for 10 more minutes. Why even I had turned off the fan completely before turned off the engine, but after turned engine off then the fan woke up and running for 10 minutes? I don't understand the logic here.
 

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Not blower motor. There is a small fan IN THE CONTROL PANEL. Pull it out and see.

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Discussion Starter #9
Not blower motor. There is a small fan IN THE CONTROL PANEL. Pull it out and see.

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Why do I need to pull the little fan out and see? If this fan suppose to run for 10 minutes after engine turned off then it's normal.
 

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BMW 320i 2002 e46 5spd manual RHD
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Why do I need to pull the little fan out and see? If this fan suppose to run for 10 minutes after engine turned off then it's normal.
No its not normal for it to make noise, you supposed to service stuff that make noise or fix it, leave it like that and it will get worse

And no not the blower motor, the fan as stated above is on the circuit board of the hvac you need to clean it and service it, it has no bearings but bearing grease helps smoothen the shaft so it doesn't make noise due to friction...
 

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Why do I need to pull the little fan out and see? If this fan suppose to run for 10 minutes after engine turned off then it's normal.
C'mon the guy just gave you the area where your noise is eminating from.
If you'd looked in the archives you'd also see a thread (also going on now BTW) about the same noise.

There's a tiny fan drawing air across the PTC resistor (just behind the round grille) for auto temperature control/compensation.
You'll also likely find the grille on back clogged with lint.
 

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Discussion Starter #12
C'mon the guy just gave you the area where your noise is eminating from.
I was not arguing with him; I just try to understand the logic of why need to pull it out. All moving fans makes some noise, relatively. My ears can detect a tiny noise of a normal running fan, and so the noise I have might not relate to dirty old bearings. I understand him now about cleaning/greasing the bearings to reduce the noise, but it was not made clear of why I need to pull it out in his post.

Thanks for the suggestions everyone.
 

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Guess you still dont really fully understand, i noted that there is NO bearing's, just a shaft that needs grease, anyway after all these years its bound to make noise, its up to the driver to decide if a service is worth his time.
 

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In the 4th post I recommended that you pull the control panel out and clean out the small blower/fan and air path from the little grille on the front to the blower at the back. The tiny blower wheel will be caked with dust and lint. This causes it to be imbalanced and make noise as well as reducing the airflow over the interior temp sensor. Lubricating the motor bearings will some light oil would be good if you can access them.

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Discussion Starter #15
There is a small fan at the back of the hvac control panel. It draws air in through the little grill on the front for the interior temp sensor. It runs after the car is shut off until it goes to sleep (16 min). If yours is noisy, it probably needs to be cleaned out. Remove the control panel and blow it out with compressed air from the front and back.

Sent from my S61 using Tapatalk
Sorry that I completely missed this post and continued asking "strange" questions. This post has the perfect answer that I was looking for.

I appreciate your help and again sorry about this.
 
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