Ok, I know you electrical geniuses will get this one easy.
1990 Crewcab 7.3 with ATS turbo 40,000 on engine(yes, 40K).
All of a sudden the water temp goes full hot (all the way to the peg as if shorted), the engine lite comes on, and burning plastic smell. Checked under the hood, and the glow plug controller bowas moved to the left valve cover to make room for the turbo)is hot and ground wire to it was smoking.
Note: engine was not really hot, just reading that way.
Removed glow plug controller and cleaned all contacts, replaced ground wire terminal, and re-installed. At the turn of the key, it still sends the engine lite on and the temp guage to full hot intermittantly, but the two large ground wires dont get hot now. The controller clicks on and off rapidly at times causing the water temp to bounce. I have replaced the thermostadt and the temp sender just to be sure.
I hate to spend 160 dineros if the controller is not the problem. Why is the water temp interacting with the glow plug controller and the engine lite?
Any help is highly appreciated.
This one is twisting my brain pretty hard.
Thanks!

 

There should be a water temp sensor especially for the glow plug system screwed into the intake somewhere. This temp sensor has about 5-6 wires on it. When you find it, check the harness for fused wires.
Phillip

 

The Glow plug controller uses water temp to determine if it needs to turn on the glow plugs or not. I had a similar problem with my 86 the Engine Temp light would come on and the truck was a bear to start half the time. I finally wound up replacing the controller on it. We have different controllers though. A neat thing I found out though. I went to a You-pull-it yard around here and thought I would try a used one before I shelled out the long buck and paid 2 bucks for one. I went back out and got 3 more for that price I will buy them all day.

Brad Godkin
1986 F350 CC/SRW
6.9liter/C6