When the gauge first failed to register the engine temp, my immediate thought was to replace the coolant temp switch. I go to Pep Boys (i know, i know, it should have been the dealer or a better parts place) simply out of convenience. The guy gives me a temp sensor. I was surprised that it was PLASTIC and also that it had two connectors rather than just a single point. He says that's the only one listed. When i checked the Chiltons manual, they listed the procedures for checking that sensor and make no mention of any other type of switch or sensor for the temp gauge. It lives in the right place - just above the thermostat housing so i figure it must be the bad part. After installing it - no change. So, then all the above posts about how i suspect the gauge etc..

Well, before i pull out the cluster again, i take one more look under the hood. Just to the right of the distributor (as you face the engine) there sits a sensor in the intake manifold that looks like the "traditional" type coolant sensor i've always known with a single connector. I call the dealer and ask if there's a seperate coolant switch just for the temp gauge and he says yeah...that's it! Great....i do a quick test by grounding the wire and the gauge pegs hot. I replace the switch and now the gauge works fine.

Thanks to all you guys that helped with suggestions!

TD
'92 F150 XLT / 5.8L / 4x4 / 129,000