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E36 M3 (1992-1999) {Euro - S50 B32 321hp @ 7400 rpm} {U.S. - S52 B32 240 hp @ 6000 rpm}
Total Produced: 71,212 - Years Produced: 1992 to 1999


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Old Thu, May-31-2012, 12:23:04 AM   #1
BD700
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Default E36 Aux Fan diagnosis, strange results...advice needed!

Please offer advice, I'm confused!

I'm trying to diagnose why my Aux Fan is not working on my 99 E36 M3.

If I apply 12 volts to the Aux Fan connector only one combination of the 3 pins will get it to spin (seems like high speed). Any other combination of the pins produces nothing. Is this normal or is the fan the system failure?

If I jump the plug terminals from the radiator sensor, I can hear both relays click.

I replaced both the 5 amp and the 30 amp fuses in the under-hood fuse box.

Thanks!

Brian
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Old Thu, May-31-2012, 12:33:04 AM   #2
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Default Re: E36 Aux Fan diagnosis, strange results...advice needed!

If you get 12 volts at both pins of the aux fan plug when you jump the temp switch then it would be the aux fan itself. Very common on these cars now it would seem. New ones cost around $200. I would advise not to use the AC until you get it replaced if only the high side is working. Continued use of the AC without an aux fan can cause damage to the compressor.
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Old Thu, May-31-2012, 12:48:08 AM   #3
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Default Re: E36 Aux Fan diagnosis, strange results...advice needed!

White-Hot, Thank you for the quick reply.

I just checked and I am getting 12 volts from both relays to the plug that inserts into the Aux Fan. Strange (to my admit-tingly amateur self) that it still wouldn't power the fan at all, when I could get it to run (one setting) off jumping to the battery though.

If I did start to damage the compressor(I believe by increased pressure) is there a way to release the pressure, or will it subside on its own? I'm learning as I'm going with A/C systems today.
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Old Thu, May-31-2012, 01:01:04 AM   #4
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Default Re: E36 Aux Fan diagnosis, strange results...advice needed!

In the short term it is unlikely to do damage, but over a prolonged period of time it will. I for one don't like to take chances so when the aux fan was bad on the coupe I didn't use the AC till the new one arrived. YMMV

I had a problem with my plug not making good connection with the aux fan receptacle. I cleaned both sides with contact cleaner and then slightly crimped the female contacts and that fixed the connection problem. Not sure if that will remedy your situation. In any case, if you are getting 12 volt at the plug but only one speed of the fan is working then you have a failure of the fan motor itself. Sounds like you have eliminated all other possibilities (relays, fuses, etc.).

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Old Thu, May-31-2012, 03:52:32 AM   #5
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Default Re: E36 Aux Fan diagnosis, strange results...advice needed!

Thanks again,

For the immediate future I won't be using the A/C unless I'm cruising over 50 on a freeway, maybe not even then. The 90 degree commute in Dallas traffic is not going to be pleasant though.

I tried cleaning the contacts, but I'm too chicken to take the plug apart to crimp the female ends and trust that it would be in good working order after I was done with it. Thank you for the suggestion.

Unless someone had a similar experience and found an alternate solution, I'm going to buy a new fan and just replace the relays anyway while I'm at it. They are 13 years old after all. The rest of the cooling components have been replaced 20K ago at 74,000 mi. No complaints, would have been nicer if it failed in the winter though!
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Old Thu, May-31-2012, 06:37:25 AM   #6
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Default Re: E36 Aux Fan diagnosis, strange results...advice needed!

Do both the relays still click?
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Old Thu, May-31-2012, 09:32:49 AM   #7
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Default Re: E36 Aux Fan diagnosis, strange results...advice needed!

First the AC compressor has both a high and a low pressure switch. If the pressure gets too high, it shuts down, and if the pressure gets too low, it shuts down.

If your pressure switches are working, you won't hurt anything.

For now, you could wire your fan to come on with the engine. Again, you won't hurt anything.

Keep cool.
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Old Thu, May-31-2012, 09:37:46 PM   #8
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Default Re: E36 Aux Fan diagnosis, strange results...advice needed!

Quote:
Originally Posted by white-hot View Post
I had a problem with my plug not making good connection with the aux fan receptacle. I cleaned both sides with contact cleaner and then slightly crimped the female contacts and that fixed the connection problem.
I had the same issue. Glad I'm not the only one.

IIRC, one pin is ground, one is low speed, the other is high speed. Sounds like your fan is only working on one speed.

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Old Thu, May-31-2012, 09:49:25 PM   #9
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Default Re: E36 Aux Fan diagnosis, strange results...advice needed!

Both relays click and supply 12 volts independantly to the harness measured at the plug that connects to the fan. Strangely I can't get the fan to run from the harness power, but it will run on high speed only if I hard wire to a car battery.

In my research I found that BavAuto even sells a kit with a replacement harness connector and pins for $18 or so.
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Old Thu, May-31-2012, 11:05:47 PM   #10
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Default Re: E36 Aux Fan diagnosis, strange results...advice needed!

Sounds like BavAuto, sell what you could buy at the dealer for $8 for $18! Good work if you can get it!
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Discussing E36 Aux Fan diagnosis, strange results...advice needed! in the E36 M3 (1992-1999) Forum - {Euro - S50 B32 321hp @ 7400 rpm} {U.S. - S52 B32 240 hp @ 6000 rpm}
Total Produced: 71,212 - Years Produced: 1992 to 1999 at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)