Problems with Temp Gauge/over heating

[Prophet78]

Well, we have been hunting down this problem for a little while and last night we found out what it was. I thought the car was hot and was overheating but the car was actually running normal temps The gauge wasn't reading correctly.

For those of you whose gauge shoots perpendicular when the car is turned off and/or if you think the car is running hot. If the car is running up in the "R" "O", or "N" you may have a bad ground.

Last night we spent time switching out the fan servo and testing voltages on the sensors to find out that there was a bad ground in the car. We were lucky and found the ground that was causing the problem.

I hope this makes sense, if not I will explain further.

-Jeremy-

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E-Mail Address: mailto[email protected][email protected]</A>
Webpage: http://prophet780.tripod.com
'93 Red ATX "Red Phoenix"
Rebuilt "Ford Quality Rebuilt Transmission" w/ Shift Kit
SHOShop CAI W/K&N
SHOShop Front STB
190 LPH Fuel Pump
Koni Inserts
Eibach Springs
Blazer Modded Fog Lights
Taylor 8mm Spiro Wires
SHO Filler decals
Fish Tanks
225/50/16 BFG GeForce T/A KDWS

 

[fricker66]

I might need some further explanation from you. My car usually registers on the cool end of normal but will sometimes rapidly fluctuate a letter or two. I've figured this is do to the sending unit going bad. Now the other issue is that the gauge will quite often shoot perpendicular when the car is turned off. I first noticed this after we changed the thermostat a couple of years ago. I tested the engine and since all signs showed normal temps I've ignored this issue. I'm interested in knowing where this ground issue was in your car. Any further help would be great.

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Frederick Ricker
89 Black w/ 78k mi
Stock w/ 91 Slicers

 

[Prophet78]

This is what I was experiencing. While driving the temp would sit on the "M". Then when I would sit for more than a minute the temp gauge would rise all the way up past the "O" to the "N" and if I drove for a while after that the next time I would sit the car would go up to the "N" and then drop down after the fan kicked on. A few times right before the fan kicked on the needed would fluctuate and jump then drop down to the "R". This is what caused my concern. Also I thought something was up when the needle would go perpendicular after turning the car off.

I took it to Toolboy79 and he started the EEC-IV diag and found that the car was running at idle the temp would rise up to the "N" and kick the fan on. The readout showed that the fan was kicking on at 213 degrees. We then found out that, that was the normal temp for the fan to kick on. So then we started doing tests on the temp sensors and voltage readouts on the sensors.

I little more information. The car always seemed to "over heat" at night. Never during the day. Well as we were testing another Ford Tech came over and turned my autlamps off. The gauge dropped. After a little more investigating, we found that the gauge would shoot up a couple letters when anything on the dash was turned on. Things like the lights, autolamps, rear defroster and I think the EATC.

After that we knew that there was a bad ground somewhere. Toolboy and this guy tracked it down to the passenger side strut tower. There are a few grounds that are bolted down and the one that was held on with a sheet metal screw was the culprit. It is an "eye" looking faster with a wire connected. Turns out that if you have done a lot of work where you pull this ground out it will loose its ability to ground properly. They cleaned the ground and moved it to the bolt right next to it.

One more thing. My car is an ATX and the MTX's may be different.

Now my car runs in the "A" and rarely touches the "M"

-Jeremy-

 

[fricker66]

Thanks for the extra info. Now I'll know what to look for when I get some extra time. I'm pretty sure I've got the same ground you fixed on my MTX. Often wondered if I was the only one whose car would register past H as soon as it was shut off.........

 

[Prophet78]

There are a few more of us who have/had this problem. That is what sparked my attention even more was when someone mentioned it here on the forum. I didn't read the thread, and I didn't do a search on it.

-Jeremy-