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Heres the problem. I Stoped fast & the Pos. Post on my battery hit fender. Tryed to shut off the key but the truck kept runnin. I found the problem and moved the battery back. Anyway my fuel cabel melted and fried voltage reg.
Fixed both and noticed temp was runnin hot. It Idels at normal temp But when I drive it It gets hotter. When you stop and let it ldel for 35 seconds It cools back down to normal again.
Strange.
So here is what i did. I installed a New thermostat, New Temp sensor sending unit. New gage, I even tryed changing the Thermosensor Controller under the dash, I changed the whole dash out. with no luck
Gage still says it is over heating But the truck really dose not seem to be.
So I pulled the thermostat and the gage stays at normal temp when I'm driving and drops below that when siting at idel.
I'm stumped.
I would like to fix it the right way. If anyone has figered this out plese let me know. I read here one guy had the same problem But had no luck fixing it. So someone out there has got to know how to fix this

Thanx all
Doron

I did the same thing.
Mine seems ok now, after I ran a new ground wire from the battery to the chassis.

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77 2wd - Back on the road
05 Ford Five Hundred

"Love endures all things, Love never fails." - 1 Cor. 13:7,8.

might try running a ground off of something in the dash too. They don't really have a good ground for that junk. Seems to help with some gremlins...

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Resident lurker

Thankx for the info.
I'll give it a try and let you know

Both the temp gauge and the fuel guage operate off of a little regulated voltage supply built into the gauge cluster. It is supposed to put out something like 7 volts to the gauges for them to operate correctly. What I think might be happening is something in the charging system is still not right and the battery is getting overcharged. When you sit at idle the alt doesn't put out as much juice, so the voltage comes back down where it is supposed to be. If I had to guess I would say you might have a problem in the alternator. Sounds like that is the only thing left that has not been replaced. Either that, or the wiring harness is shorted and putting 12v into the line for the temp gauge. The bundle that goes across the top of the firewall carries the main alt wire and it may have hooked itself to something else. It might also help to look at the fuel gauge for any odd behavior since they are powered by the same source. Reading high, or swinging past the F mark would be what I'd expect.

Unless I'm really tight on money and really sure I know the problem, I always try to replace the reg and alt together. Problems in one can cook the other, so I've tried to err on the side of caution and treat them as a unit.

If you have a voltmeter, try checking the voltage at the battery. Run the RPMs up a bit for a minute or so and see you get more than about 14v. If you do, then you know its in the charging system.

I picked up an infrared thermometer a while back and found it surprisingly helpful for troubleshooting cooling systems. You can read the temp of the thermostat cover and get a pretty close reading to what the gauge sender is getting. If you time things right, you can read the opening temp of the thermostat that way too. Something like that could tell you if you are truly overheating or whether it is just an instrument problem.

Hey thanks for all the info.
This will give me a few more thingh to try.
I'll keep you informed

DoRon

My luv diesel did this for a long time...I changed everything out checked charging systems and didn't solve the problem...Then i decided to change clutch fan that cools radiator....fixed it havent had another problem just a idea for ya....Hope it helps