So Im 18 years old and I just got this car about 2 weeks ago. I’ve went through everything using a reproduction copy of the GM shop manual from ‘78. But everything I have tried doesn’t help with the temperature gauge. I replaced the 20 amp huge cluster fuse and it made all the previously non-working dash lights and guages work again, but not the temp gauge. Took the old sensor out and replaced it and still nothing. So now I have confirmed that it has power by putting a ground on it, but when the car starts and gets warm, nothing. So I would kindly ask for some help because I have wanted one of these exact cars for very many years and have built up a knowledge on them, but can’t get this one figured out.

 

Disconnect the wire from the sensor and ground it to the block. Turn the ignition key on, Does the gauge peg to full? If so the gauge and associated wiring is working. Make sure the block is grounded to the frame/body with proper grounding strap for that car also.

If it passes this test, then it's usually something related to the sensor. Perhaps you have the wrong type of sensor. Sensors for idiot lights are open (no contact) until the engine reaches a preset overheated point. Sensors designed for use with gauges have variable resistance. As the coolant changes temperature, this is what makes the gauge needle move to different positions.