My temp gauge started acting up the last few times I was able to drive the car. It would be running at operating temp, then drop to minimum for a second or two, then go back to normal.
The time it would stay at minimum began lasting longer and longer. Now it won't come off min at all (except, of course, when it does the normal starting high peg).

I did a search to test the sending unit.
I found that the pin for the gauge should read about 1365 ohms @ 100*F and the other pin should read open (the one for the light).
BOTH pins read open all the time.
Does this mean that the sender has gone bad?

I need to fix this before going to the club meeting Saturday. Any help would be appreciated.
Thanks,
Egor

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"Of all the things I have lost during my lifetime, I miss
my mind the most."

That connector gets cooked by the manifold heat and gets sloppy. You may be able to tighten up the pins, or maybe you will need a new one.

As long as you are on the right sender - the one with the side notch - yes it is bad.

Note - Many times ppl go to the parts store and the kid behind the counter tries to sell them a CTS (Coolant Temperature Sensor) and then the plug that fits the CTS since it is different than the gauge sender plug. The correct one, and the only one that will work is the one that has a connector just the same as your existing combo temp gauge/temp light sender.

RESULTS:
I always like to finish off a topic when I can, so

I found the right sending unit and installed it this morning. The gauge is working again, although it seems to be running a little warmer than the original.
I don't know if it is really warmer or if the old sender was showing cooler than real because it was going bad for some time. I will have to borrow a laser
temp reader to check.

Thanks for your input.
Egor

quote Originally posted by Egor: I will have to borrow a laser temp reader to check.

Or you could use an OBD-I scanner or WinALDL to read the temperature reported by the ECM coolant temp sensor. That would be more accurate than an IR thermometer.

[This message has been edited by Marvin McInnis (edited 09-27-2014).]

I've found my Harbor Freight IR unit to be pretty accurate if I point it at the brass base of the sending unit. I drive to get the car up to operating temp, then park and let it idle until the cooling fan comes on. I quickly check the base of the sending unit to see if it's close to where it should be. That also assumes that the fan switch is working properly.