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dash16 · Joined: 22 Aug 2007 Posts: 255 Location: Cali Cali

My aux fan usually has to be trigger by my turning on the AC when idling in traffic because it will not flip on by itself.

While returning to my car one freezing night, i drove my car home and the fan turned on by itself.

When I returned home, i was surprised to find that the fan remained running after I had switch the car off.

I figured it would be fine. I returned to my car 10 minutes later, the fan was still running. It could not have possibly have been triggered from heat since it was freezing cold out.

I unhook and hook the battery and the fan did not re-trigger.

What could have possibly happenned? Electrical bug?

Is there a way to run an electrical diagnostic on my car?
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1987 Porsche 924S Black/Black. 5-spd.
Options: AFX C79 261 398 423 650 651 657

1987 Mercedes 190E 2.3-16 Cosworth Pearl Black/Black. 5-spd.

STUTTGART PREVAILS

bcblase · Joined: 23 Oct 2007 Posts: 574 Location: Winchester, VA

Sounds like you need to replace the fan temp. switch located on the top left side of the radiator. My fan turns on a bit early, because I think it was replaced with a lower temp switch. I have the new switch with a higher temp rating, but I have not had a chance to install it yet.

BC
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1987 Porsche 924S - track toy
1986 Mercedes 190E 2.3-16v - autocross
2007 F-150 5.4L Lariat Supercrew - tow beast
1994 Volvo 850 Race Wagon - 24 Hours of Lemons Car
2001 BMW 325xi - daily driver

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

Red did this. . .fans ran the battery down because the relay was bad.

If you swap the relay, inspect the fan wiring harness. A short there is what actually messed the relay up in Red's case.
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Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

joecitizennn · Joined: 12 Sep 2005 Posts: 2096 Location: no mans land

The next time you shut off the car and the fan is running, reach down behind the drivers headlight pull one of the wires out of the thermofan switch to see if the fans shut off. They should

Next unplug both wires and put a jumper between them to see if the fans come on when the wires connect and shut off when the wires disconnect. If this is the case the wiring is ok and the problem in in the switch.

Oh yeah, you may have to remove the airbox to be able to plug them back in. Dont say I didnt warn you.