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New here. Question about what fan noise could be..

2K views 3 replies 2 participants last post by  djb25 
#1 ·
Hi, I'm new here. I got a 92 325i a couple of months ago, 80K miles, great shape.

Anyway, I was having a couple of problems and so i read a bit on this forum and got a bently and went on my way. I fixed 3 broken parts in the sunroof and am waiting on some grease so it slides better more easily, but now it closes and opens perfectly. I changed out the AC microfilter, the old one was disgusting. I also took apart the interior door panels to fix some bubbling and had a piss poor time trying to get them fixed, i have one more to fix that's bubbled really bad, does anyone have any suggestions for that?

The problem I have that I can't solve is this, I have an electrical short that drains my battery in 6 hours or so. I know the battery is good, the alternator will generate plenty of power (I just disconnect the battery cable every time I park somewhere, it looks real cool popping the trunk to disconnect the battery cable and reentering my radio code and time for the OBDI).

Anyway, with the battery connected, there is a fan that runs that's noticeably loud. This is without the key in btw. I took out my air intake right up to the mass airflow sensor. The fan noise seems like it's coming from INSIDE the air intake, or at least the noise carries very well through it. I'm pretty sure this fan shouldn't be running without the key in so I think it's the culprit. What the F fan could it be back there?

If you want any more pics or need some kind of test, message me.

I've also disassembled my sunroof and successfully put it back together, so if you need any help with a sunroof fix for a 92, message me i'll be glad to tell you what I did.

Cheers - Nate
 

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#3 ·
So after some further digging, the engine cooled enough that whatever fan was running stopped. Is it normal for a fan to run with the key out of the ignition and the engine off? Could I have a faulty temperature sensor somewhere?

The current draw is maybe 2-300 miliamperes with the fan not running.

I'd take wild speculation about this, whatever you can offer. :(

Cheers - Nate
 
#4 ·
I'm surprised no one has bothered to reply to your question. Sometimes I wonder about this forum - there's way too many people concerned with the coolest shift knobs they can get, and not nearly enough people to help with tech questions.

Anyway, the fan that is running might be a couple different things - first I would say its probably the electric engine fan on the radiator (these cars have both an electric and belt driven fan). However, since you heard the fan from somewhere behind the airbox, I'd guess it's the blower fan for the HVAC system. These cars have some sort of ventilation feature programmable through the onboard computer that "vents" the car after the ignition is switched off. There's more info on this in the user's manual.

By the way - if the fan were actually the electric cooling fan (for the radiator) there could be a bad temp sensor. This happened on a 944 I had a long time ago - the switch went bad, and sometimes the fan just wouldn't shut off. Killed my battery a few times.

Good luck,
Damion
 
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