coolant temp gauge gone haywire!

[servohead]

all the sudden: went to the store and got back in the car, still at operating temp minutes after startup the coolant temp gauge started wavering up and down often all the way to the hottest limit and back down to normal again, got the "coolant overtemp" message and bell. I checked the connector, unplugged it and replugged it in, no corrosion, and the problem persisted.Then all was well for the rest of the 10 minute drive. no pcm or any other codes set at all.

Is it likely that I have a faulty engine coolant temp sensor? is that a common occurence?

[leadfoot]

Are you certain the car isn't overheating? Coolant level OK? Anything stuck in the radiator?

[servohead]

Originally Posted by leadfoot

Are you certain the car isn't overheating? Coolant level OK? Anything stuck in the radiator?

absolutely, the temp gauge worked fine for the 15 minute drive to where i was going until shutdown. 50 miles ago i checked the radiator when I did the oil change. when the gauge acted up it seemed to point right back to 185 when it stopped freaking out, including on the digital readout. i Know overheating is a problem, but that wasn't it this time.

[c4c5specialist]

HI there,
There is a resistance table you can use if you have an ACCURATE digital ohmmeter.
You would use a noncontact infrared thermometer and the ohm meter to determine if its good or not.
Allthebest, c4c5

[servohead]

Well, I fixed it! I bought a new temp sensor and when I was replacing it I found coolant leaking out of the sensor internally as you had stated c4c5. This must have shorted out the sensor causing the whole issue. now all is well and the temp gauge works fine!
When I replaced it I used my hose pinchers on the upper and lower radiator hoses, and only a little coolant came out when I replaced the sensor - saved me from having to drain and refill the whole engine.