1994 Chevrolet Silverado Repair Question
Engine coolant gauge
Answer
I had the same problem with my 1995. It is the connection at the sensor that is the problem. It relies on the ground going through the sensor which is modulated by the temperature of the engine block. I had to push in and wiggle the wire at the connector (with the engine hot) until the guage starts working again. I eventually tired of the burns and inconvenience of that game and repinned (crimped and soldered a new pin to the wire) the connector. That worked for a while but, finally, I hard-wired the sensor and put a Duesch connector inline so I can disconnect it if need be. I think it is a combination of the plug anchors and the way the pin locks into the connector causing intermitent opens in the circuit.
Check grounds to the circuit.
Sorry for the mix up here. I did not read closely and thought you were talking about the oil pressure sender for some reason. J&N obviously got it right here. If you need help on the proceedure for testing this circuit and it's grounds, I can help you there.