Fake overheating?

Icannap1 thank you.

I had success, sort of. I used the jumper cable connected to the battery ground and put it in the passenger window, removed the instrument cluster and found the one ground on the top rear of the cluster. I started the disco and let the temp gauge spike and then touched the jumper wire to the instrument cluster ground and HOORAY the temp needle went to normal.

I then removed the drivers kick panel and touched the jumper wire there and HOORAY, temp gauge went to normal, dash lights went to normal brightness and fan speed went up to normal speed?

I tried to follow the large gauge black wire out under the hood. I removed the air filter box and cleaned the ground wires near the fender, but that did not correct the temp gauge.

It was getting ready to rain, so I ran a 10 gauge wire from the battery negative into the firewall and attached it to the grounding bundle in the driver's kick panel.

All is working as it should.

I did remove the battery ground cable at the frame, and the motor cable at the frame, but didn't have time to do the motor ground at the engine side.

I'll look at your diagrams, but I would really like to know where the grounding strap in the driver's kick panel go out under the hood and where they pull ground from? It looked like they might go behind the engine near the firewall and down to the transmission or engine?

Any thoughts on where those grounds pull from would be helpfull.

Thanks for all the help. Maybe not the "correct" solution, but it is workable for me for now. If I track down the exact ground problem, I'll be sure to post it. I found a lot of posts on the web about temp gauge spiking with headlights and fan on.

I did clean E109 with no improvement prior to adding the temp ground. I will check E102 and E100.

It looks like E100 is different from the battery negative ground to chassis that sits below the battery box? That was the first ground I checked and cleaned?

German and Icannap1 THANK YOU !!!!. Yes, it was E100. The bracket was completely loose on the cable and corroded. I've attached a pic.

I removed the battery this evening, wire brushed the cable and the clamp and then reattached and soldered the clamp back in place.

I re-assembled and removed the temp ground. Ran the disco till hot and turned on all accessories. The lights are nice and bright, heater/AC fan running on high speed. No more popping and cutting out radio when switching fan speeds and dash lights nice and bright!

Temp gauge is solid and steady at just below mid point and ODB scanner confirms 180 degrees at idle with AC on. Sounds like success.

I also confirmed the temp ground is not needed any more by touching it to the negative battery connector a few times when all the accessories in the cab were running and no sparks or arcing happened!

Hopefully if someone else is searching for this problem, this thread helps.

Regards!

Picture after cleaning. It was really hard to get solder to take so I had to put quite a bit of heat on the cable. I trimmed back the insulation about 1" on each side of the clamp and re-taped them. Should hold up for a while.

The underside of the nut and the post were clean. I didn't need to clean up the top side of the nut. The clamp discolored a bit from the heat, but it was nice an shiny before applying heat and solder.

Thanks again