After getting all the electrical working on the Jeep, I noticed that the only gauge not working was the temperature gauge. The gauge would always keep in the “Cold” region no matter how hot the engine or sensor got.

The factory service manual says the resistance values are for the gauge and sensor are:

Cold engine is supposed to be around 73 ohms off the sensor, 23 ohms for operating temp, and 10 ohms for hot.

I taped a thermocouple to the sensor body and measured the resistance of the thermistor sensor.

At ~87F the sensor is measuring ~192 ohms. That is way to high! But lets heat up the engine and see what we get.

With the engine heated up to 151F the sensor is reading 66ohms. This is barely off the “Cold” mark the service manual says.

To test the gauge. I got a 22 ohm resistor and a 10 ohm resistor and “simulated” the sensor with them. These resistors moved the gauge to the appropriate spots! So the gauge is working correctly.

Finding a sender/sensor that works for this seems to be tough. Jeep used a couple different sensors and gauge combos over the years. According to Quadratec customer service, Crown’s J3177594 has the correct range.

I got this part on order and lets see if it works!