Temperature sending unit: how does it work?

I'm trying to get my temperature gauge working in my '55 (cluster gauge / 134 F-head ). I purchased a replacement sending unit and have it hooked up correctly (i think) yet it never registers more than even a miniscule movement above dead cold. Does the sensor's ability to ground the electrical current increase or decrease as heat rises? Have I cranked it in too tight?

 

sounds like gauge might be bad.

 

The sending unit has a resistance that varies with the coolant temperature. Typical range is 10 to 100 ohms. You can momentarily ground the wire to the sending unit and watch the guage needle for movement. No movement of the gauge means a broken gauge or faulty wiring to the gauge.

 

If the guage is bad, can it be repaired? Or do you have to get a complete new cluster?

 

Not likely.They're not made to be taken apart, and the wire in the little coil that moves the needle is very fine. I'd expect a broken wire to be the usual failure mode. The gauge can be replaced separately.

Does the fuel gauge work? Not sure about the earlier Jeeps, but the later Jeeps have a voltage regulator in the fuel gauge that supplies constant voltage to both the fuel and temp gauges. If the fuel gauge works, then it's likely the problem is the temp gauge.

 

My fuel gauge works fine, but the temperature gauge only moves a fraction off of cold, much like the first post. Didn't want to go to a new cluster, due to the double numbers. Mine has the original singles. But, I guess no real big deal, as I have lived with this for some time now.

 

Mine was doing the same...... The thermostat was stuck open.......Now I can get up to a cozy 180.

 

Just replaced the thermostat?