i know this is a common problem as i have seen it before on another Ford (same year) but I can't seem to search the archives (wont let me). My coolant temp gauge bounces all over the place and never gets up to full operating temp even on hot days. It gets about 1/4 the way up then drops down near the cold line. I have already replaced the thermostat with no change. I was looking through a parts book at Napa and it didn't list a gauge sensor just the temp sensor for the PCM. I changed it anyway seeing as the data might come from the computer with no change. I know the data doesn't come from that now, as i tested it when i had it out.

TIA,

Cort
93' F250 7.5L 4x2

 

My f-250 temp gauge acted the sameway on a 1988 model year. I replaced both the alternator & temp gauge portion of the instrument panel ( one peice ) and it solved the problem. Picked up the part at a wrecking yard for 10 bucks.

 

Normally it's the thermostat. Your temp gauge should move slowly from "really cold" to somewhere in the normal range, then park there, maybe with a very slight swing.

When my thermostat went bad, my temp gauge would swing from "N" to "L" back and forth, about every 10 seconds.

 

and tested old one for operation (boiled in water) and it worked! Maybe it is the gauge- but i guess my main question is, where does the gauge get the reading from? it's not the coolant temp sensor on top of the engine.

Thanks again,

Cort

 

I can't help you on temp gauge sensor location on a big block.

Your description of how the temp indicator guage behaved was exactly like my temp gauge. I only replaced that portion of my instrument panel to repair my alternator gauge which included the temp indicator as well.

It was merely an added bonus when I noticed the temp gauge was now indicating properly.