Overheating When Idling

[Tommy]

Originally Posted by zzmac

I used the jumper cables and both fans work. When I remove the negative jumper cable the fans don't turn on.
Next step? :-)

That tells me the fan is not properly grounded. It could be at the fan or where it connects to the ground source. This assumes the relay provides +12v and not the ground.

P.S. If you can't find where the ground is bad, you can run a temporary ground wire from the fan(s) to a known good ground to hold you over until it is convenient for a permanent fix.

[NROTOXIN]

The jumper to the fans shows that the fans do work, which is good but does not test the rest of the circuitry consisting of the relay, two 20A fuses and the thermal switch. The relay is behind the dash, the fuses are on the drivers fender well. When idling, the only indication that my fans come on is my amp gauge goes just negative of zero. The override switch simply shorts the thermal switch and relay coil (86) to ground that then energizes the relay coil. If you don't have a ground connected at the thermal switch or brn/blue at that same switch, nothing will work. What's equally important is your source voltage to the relay (30), connectors at the relay (87) that come from the two GOOD 20A fuses.