Ok temp gauge trouble

[k_n_browning]

Ok the gauge works if I ground out the sending wire it go's hot.But with or without the wire on the sending unit.The gauge drops below cold.Thanks Kevin

[franken]

Is there a question in our future?
You verified the wiring and the gauge works. What do you think the problem is?

[Blue GMC]

Does the gauge just peg out or when at running tem live in the hot zone?

I would have someone using a digital gun take temp readings of the radiator, and the fluid coming in and out of the engine. Mine shows a wierd reading as well but have verified that the gauge is off and at 3/4 to hot is perfect opperation temp. The factory gauges are old and can act crazy.

[Prescott]

I like to replace the temp sender. They're cheap and they wear out. Try not to use too much sealant, as the threads are an electrical connection.

[k_n_browning]

No it pegs below cold and never move.does this with or without the wire on the sending
Unit.Turn the key off and it will go to cold.Turn it back on and it drops below the cold mark.

[knomadd]

Sounds like your gauge might be out of whack. I'd try a new sending unit first, like Prescott suggested, but if that doesn't work, maybe you need to replace the gauge.

[Daddy'O]

My guess is the sending unit is open. The sending unit is a variable resistor to ground. As the sending unit heats up it becomes less resistive causing the temp gauge to deflect to the hot side. When you grounded the sending unit wire you have zero resistance which caused the temp gauge to fully deflect to the hot side. If you have a multimeter you can measure the resistance of the sending unit (engine cold and OFF) by measuring between the tip of the sending unit to a good ground. If it measures extremely high or open then you should replace it. Let us know what you find.