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Trouble-shooting Auxiliary Fan -- Input Needed

I've really only driven my '95 318is (M42/5sp) in the winter, so I haven't paid much attention to my A/C. Last week I took it out in 90+ weather and noticed that in stop & go traffic, my A/C doesn't blow cool. When I got on the freeway it started blowing cool again. Based on internet searching I've deduced that my aux fan might be faulty.

Following the trouble-shooting tips in my Bentley, I jumped the leads on the radiator coolant temp sensor together to see if they turned the aux fan onto low/high speed. Nothing. Bentley's next step was to check the fuses. I found a blown 30A fuse corresponding to the aux-fan. I pulled a 30A fuse from my cigarette lighter, and tried jumping the leads of the coolant sensor again. I promptly blew the 30A fuse again! I should mention that I can hear the relays clicking each time I jump the connections.

I can across one post on Bimmerforums where the poster's aux fan was actually frozen, and required replacement. At $250+ for a new fan, I would like to make really really sure that the aux fan itself is to blame. Any input and advice regarding how I can CONFIRM that the fan itself is shot would be very helpful, thanks!

Matt
Old 06-14-2007, 07:56 PM
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You can put run power directly to the fan but I would run a fuse on the leads. I recall a post about trying to repair the fan circuitry but I didnt read it thoroughly.

Ultimately, you can replace it with an aftermarket just like you would a primary fan, I think I've seen a post on that too. Since most aftermarket fans are single speed you just wire it to come on at low temp side of sensor. Actually that reminds me, the post was a question of if they could wire it to the low side or to both so it would stay on at low and high temp.
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Old 06-15-2007, 07:58 PM
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UPDATE -- I pulled my aux fan, it was pretty much seized. I took it to the shop that rebuilt my alternator and they said the magnets were toast and it wasn't repairable.

I went to a salvage yard and picked up an entire cooling fan assembly. I installed the assembly....and....NOTHING. I jumpered the connection on the coolant temp sensor as prescribed by the Bentley and I could hear the relays click (high speed & low speed), but still no fan spinning.

HOWEVER, I have NOT blown the 30A fuse this time as I had been doing before. Which leads me to believe that I have some other problem that is NOT the fan motor at this point.

Jeron -- any other advice or links you have would be a great help!

Thanks in advance,
Matt
Old 06-25-2007, 12:55 PM
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The relays are clicking but is the fan getting power.
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Old 06-25-2007, 09:41 PM
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Just a late FYI.... A fan motor off a 1997 ford taurus mounts right up to the BMW shroud.....
Also, Did you test the "new" junkyard fan? It could also be bad.
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Old 06-26-2007, 08:17 AM
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-- UPDATE --

The only trouble-shooting step yet to be completed (according to the Bentley) was to check the low speed & high speed relay to be sure that terminals #30 & #86 are getting power. I completed that test, and found that terminal #86 on the low speed relay IS NOT getting power. Everything else is getting 12v.

My next question is...can anyone make sense of the wiring diagram, below?? The top image claims to be for a '92, and the bottom for '93-'95 (I have a '95). However the relay terminals aren't labeled on the '93-'95 diagram, so I'm not quite sure how to make sense of that.



When I look at the bottom wiring diagram...I cannot understand how I'm getting 12v at the temp switch connector, but then I don't get the same 12v at the #86 socket for the low speed fan relay. It would seem to me that the temp switch gets it's power from the relay??

Also worth mentioning...with the "old" fan that was totally seized internally...I would only blow the 30A fuse when jumpering the temp switch connector. I would NOT blow the 5A fuse. Could that be because the 5A fuse somehow wasn't getting any current draw when I jumpered the temp switch connector?? Is that related to the #86 socket for the low speed relay???

Obviously, electrical diagrams are not my strength. ANY help is very much appreciated!!

Matt
Old 06-27-2007, 02:01 PM
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Just to close the loop on this...

I missed the part in the wiring diagram that called out changes in the pin position for the relay, specific to the 1995 model year. It turns out I was getting 12v everywhere I should be getting 12v.

The reason my new fan didn't work was because I mangled the ground wire boot on the actual fan wiring harness when removing the old fan. The thing was STUCK in there and it took a lot of WD40 and some serious muscle to wrestle it free. I must've damaged it when pulling...because I cut that wire out and spliced in a new one and now the fan works as the germans intended.

Thanks for all of your help!!1
Matt
Old 07-16-2007, 03:13 PM
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Old 07-16-2007, 03:13 PM
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