I have had this truck about a week.Haven't driven it much.I drove it home and about half way home the temp gage was showing hot.SO I pulled off the road to see what was the problem.I did not see hear or smell any indication of the engine overheating.I drove it home stopping several times along the way to make sure it wasn't actually overheating.I replaced the temp sending unit and the thermostat.That seemed to have addressed the problem.Tonight i was giving my wife her first ride and the temperature hand was fine then after about 20 minutes of driving it pegged.I stopped and opened the hood.Once again I couldn't detect any thing that indicated the engine was over heating.When I got home I dug out a thermometer and checked the head temp.It was reading around 160 the engine had cooled a couple minutes only.What do you recommend?Should I just pick up a mechanical gage to confirm I just have a gage problem? I really don't think it is actually running hot. I have had experience with overheating and I would not have been able to drive as far as I have without some physical indication that the engine was hot. I DON'T THINK ?? its a 73 302 F100 3 on the tree
Help

 

I`d put a mechanical gauge on to monitor it. 30 year old wiring seems to get a few flaws.

 

sounds like a intermittant short in the wiring or gauge

 

Do all of your gauges (oil, fuel, temp) read high when this happens? Could be the instrument cluster voltage regulator. My '84 Mustang has that problem and I know it's pretty common with others from that era; haven't gotten around to fixing it yet.

 

I would say that there may be a short somewhere. I just installed an aftermarket gauge on mine, took about 15 minutes and now I have a back-up in case mine acts up and if it looks like it may not be cooling enought I have a more accurate reading of what the temp actually is.

 

I had a similar problem, when the dash lights were on or the turn light indicators were blinking my temp and fuel guage would peg, turns out it was the wiring board on the back of instrument cluster was shot. I could see where the fine copper wiring assembly was broken and someone tried to patch it. I also replace the voltage regulator. Problem fixed.

 

I think its common on these old trucks. I had the same problem , installed new sender. It would work part of the time. Installed a mechanical guage in a different outlet.Never touched the electrical one again, after about two days it starts working and stays about the same as the mechanical one does. I'm going to leave both hooked up, I don't trust the original one. Thread tape on the threads of the sender can give trouble I have heard, so I install them dry. Maybe they have to be grounded through the threads , I'm just guessing.

 

Thanks for the input!
I will stop by and pick up a mech gage this afternoon.
I don't think the other gauges even work.I have been focused on the temp gauge.I'll let you know what happens.The temp gauge and some really rotten tires are really the only thing I have major concerns about at this time.I am very happy with the truck so far.