I Still Cannot Get My Aux Fan To Run

[jbondbmw]

Ok, so I have been trying to get my aux fan to turn on with my A/C for a while now.

I have replaced the radiator switch, fuses, and both relays. The fan will run if it is powered at the relay connection, that is why my buddy and I thought new relays would fix it. I assume I have the relays in there properly, the BMW roundel and part number side is facing the engine.

Any thoughts as to what my problem might be?

Thanks,
Mike

[RVAE34]

I would trace the power source that tells the fan to cut on when the a/c cuts on. Perhaps there is a problem going from the a/c switch to the relay. Just a wild guess though..

[Tdibartolo]

I just took mine out last week due to working intermittently. I "cleaned" the contacts inside the motor... I basically took it apart down to the motor and pounded it on its face (gently, of course) and watched the years of carbon dust fall out! Sprayed it with the appropriate cleaner/protector and it now works beautifully! When it would stop working, I could stick a long screw driver in and touch the fan body (if you do this, please use every bit of your common sense! DON'T touch the blades unless you want a mess) and it would work as long as I applied ANY pressure...

[jbondbmw]

I'll add some more info:

Fuse 25 (low fan speed) was blown and I replaced it. The fan worked for a little while and then stopped, a while meaning a day or so.


Either I have a bad fuse that looks okay or there is a disconnect between the fuse box and relay.

At this point I feel lost.

[whiskychaser]

I would trace the power source that tells the fan to cut on when the a/c cuts on. Perhaps there is a problem going from the a/c switch to the relay. Just a wild guess though..
I think you are looking for a switched ground at pin 85 of the low speed relay to energise it. This will come from the AC pressure switch or from the low temp switch on the rad.
The diagrams here seem to suggest the pressure switch brings in the high speed fan. Thats either wrong or I have got my silly head on:
http://www.wedophones.com/BMWManualsLead.htm

[RVAE34]

The high speed fan relay is only supposed to work when the engine temp starts to get high iirc.

[TSMacNeil]

The high speed fan relay is only supposed to work when the engine temp starts to get high iirc.

Correct, the A/C should always bring the AUX fan on low speed. Only when the high temp sensor on the radiator commands it will the fan operate at high speed.

For OP- does your A/C work at all? If it does, and you can power the fan via its' relay...then you have a wiring/connector issue.

[jbondbmw]

Well, I just double checked the fuses again. Fuse 25 is cracked, not blown, but had a thin crack or cut in the metal. I am off to buy a new fuse and will report back.

[T444E]

You don't have spare fuses on your fuse box cover?

Also, as soon as I hit the A/C button, the fan should come on?

[jbondbmw]

You don't have spare fuses on your fuse box cover?

Also, as soon as I hit the A/C button, the fan should come on?

The fuse 25 I have is a replacement. It looks like the one on the inside of the lid that I replaced was damaged.

Yes, as soon as the A/C comes on the fan should turn on its low speed.

I got some new fuses but it is t-storming now so I'll swap it out tomorrow.

[jehu]

You don't have spare fuses on your fuse box cover?

Also, as soon as I hit the A/C button, the fan should come on?

I keep a full set of all fuses in the trunk..

[paperplane94]

I cannot believe no one has mentioned the Aux. Fan resistor.

or have I misread...

[jehu]

I cannot believe no one has mentioned the Aux. Fan resistor.

or have I misread...

You missed it.. he said he replaced both.

My wiring was loose I found after replacing the in line resistor.. The connection was simply not secure and the fan would not operate.. I was stumped after basically replacing everything .

I just reached for the resistor connection down on the fan with everything running just fiddling with the connection and it came on showing that the connection for the replacement resistor was just not as tightly secored as I'd thought . I firmed that up and it was good. Turned out I didn't even need the $35 yellow relay..

[paperplane94]

You missed it.. he said he replaced both.



Where...:cool

I'm still missing it.:) I wanna hear it from jbond because the resistor would definitely seem to fix his problem.

[jehu]

nevermind I somehow read your post to ask if he replaced the relays.

[paperplane94]

I saw that.

I think by radiator switch he meant this:
http://www.turnermotorsport.com/image/engine/61311378073-sm-wp.jpg

last I checked that aint no resistor, or maybe my brain is tired.

Lets wait to see what he says tomorrow.


nevermind I somehow read your post to ask if he replaced the relays.

No worries mate.
:)

[jehu]

I thought I read his previous thread about this saying he had replaced the resistor but maybe it was just someone else asking about the resistor..

It turned out to be the problem with mine..

[jbondbmw]

I replaced the cracked fuse this morning and still no dice.

I have the resistor, looks like I better put it in. I hope it fixes the problem. I don't see how since when I power it from the relay it runs, it could be the resistor, but there is nothing else to replace.

[ross1]

Check fuse 29

[jimoreno]

In my car a dirty aux fan plug made fuse 25 go. When I started looking for the issue, I disconnected the plug and found really bad looking pins so I cleaned them and reconnected thinking that was my issue. It wasn't so I pulled out my multimeter looking for voltage on both connectors (didn't knew which one was low speed) and got nothing so I checked my fuses, replaced the blown one and still nothing. Got back under the car and pushed the connector and it worked.
Just my story, YMMV

[KyleCleveland]

Check fuse 29

Yes, both 25 and 29 are associated with the aux fan. My fuse 25 was blown last week also.

[jbondbmw]

I'll double check that 29 doesn't have a small crack like 25 did. I am also going to try installing the old relays. If that doesn't fix it, all that is left is the resistor and the fan.

Maybe the fan is old and draws to much power?

[whiskychaser]

Have you tried this?:
http://www.nmia.com/~dgnrg/page_20.htm
If the fan comes on when you jumper the terminals, then it and the relays are fine. All the temp switch and AC pressure switch do is provide a ground

[jbondbmw]

Have you tried this?:
http://www.nmia.com/~dgnrg/page_20.htm (http://www.nmia.com/%7Edgnrg/page_20.htm)
If the fan comes on when you jumper the terminals, then it and the relays are fine. All the temp switch and AC pressure switch do is provide a ground

If I remember correctly when I did that, the low speed didn't come on. The high speed did. Maybe it is indeed the resistor.

Thanks so much for the link. I will work on this when I get home from work.

[TSMacNeil]

Yes. I think we discussed this in another thread. The resistor drops the signal voltage to the fan. That's why it runs on low speed. The high speed function is commanded by the hi- temp switch on the radiator. ( it effectively bypasses that resistor for high speed operations. )
If you have hi speed but no low speed, the resistor is toast.