Allrighty, here goes. The victim in question is a 1985 Monte Carlo SS, with a complete 305 TPI from an '87 IROC. The wiring harness is the stock F-body harness, with the dash connections made so that everything works (like ALDL, VSS, TCC, etc.) It's a MAF/dual fan setup if that will help anyone figure this out.

I have noticed that the secondary fan will turn on, but at random times. Also, the primary fan turns on at 200 (have the JET 200-185 fan switch), but doesn't always shut off when the temp hits 185 (scantool verified).

Anyone have any ideas on where to start debugging? The setup has been in my car for two years and 15,000 miles, and this is the first time something has acted up. I have already replaced the relays, hoping that would make a difference. So far, nada.

Can someone verify for sure...passenger side fan is primary, and driver side fan is secondary?

Thanks in advance!

 

You have the fan nomenclature backwards: the driver's side is the primary fan, and the pass. side fan is the secondary. That's probably causing all of the confusion. BTW, I recognized your name and car from the GM-ECM list, although I'm mostly just a lurker there.

 

Ah. Well, either way, the fan still behaves wierd. It will turn on sometimes right after I put it in reverse to back out of the driveway, then shut off once moving. Doesn't seem to depend on temperature either. I did notice some exposed wiring at the plug for the fan relay...maybe its grounding (or shorting) and causing it to come on at random times?

Hey, thanx for noticing! I should go through the test procedure too...gotta find my GM Wiring Diagram Book.

Thanks again!