Duke

My fans don't run in high speed. I've tried another relay that comes from a working car but no change.
So then I bought a new temp switch today but before I changed it I tried to jumper the switch connector.

I followed the procedure and image from Clark's Garage:


When I jumpered 3 and 1 nothing happened. But when I simply grounded terminal 3 the fans ran in high speed.

So the question is, is there something wrong with my thermo switch connector? i.e. should terminal 3 always be grounded and I have a bad ground somewhere? (Looked at the connector and the cables looked fine)
Or is the problem elsewhere?

I didn't change the thermo switch since it doesn't seem to be the problem.

Thanks for any ideas!
Gustaf

Waterguy

The factory wiring diagram agrees with Clarks Garage (no surprise.) Terminal 3 on the plug should be the ground; if it isn't, check to see which one is connected to ground. Once you have that, jumpering the other two plug terminals to it should run the fans on low and high speeds. If this works, the problem is indeed your thermo switch.

If none of the terminals on the plug are connected to ground, you have a ground problem. Check the grounding point on the frame rail behind the left headlight.