I have just purchased a 91 k5. The Temp guage was working fine till yesterday. Now when the key is on the guage is dead. when you turn the key off the guage moves up to the engine temp. this problem is a little past my expertise. could it be the sending unit or do I have a short in a wire.

 

Find the single wire coolant temp sensor,unlpug the sensor and touch the wire to ground if the gauge goes up you need the sensor. 90% of the time that is what you need

 

I put a new sensor in and the guage still doesn't rise. Was wondering if the electronic dash might have died.

 

Not sure but did u replace the coolant temp sensor or the sending unit? I think they be 2 diffrent things...

 

Did the sensor have 1 wire or 2?That truck should have2 coolant sensors. One for the computer that has 2 wires the other is for the gauge it has1 wire. have Did you try to touch the wire to ground and watch the gauge?