Why does my Temp gauge spike with little heat?

[xirdneh]

I start the car and let it idle
in just a few minutes the temperature gauge spiked to the top (maxed out)
the car was no where near overheating
thinking i might have a grounded wire i tested the wires and they are fine
i hooked up a temp sender that was not in the engine
i put a small light bulb under it and turned the ignition to "ON"
the gauge needle rose slowly at first then spiked to the top
i grabbed the sender to see how hot it was and it was maybe 110 degrees
I am assuming for now that the gauge in the dashboard cluster is bad
anyone else ever have this problem?

[Petros]

the gauge goes to the max when it is fully grounded, so it sounds like the wire or one of contacts is grounding somewhere. not likely the sender. could be a bad gauge, but it does not seem like it would behave that way.

[xirdneh]

i tried several senders with same result
pretty sure its not the wires (per my testing methods)
if it was the wires causing a short some how i do not see how warming up the temp sender with a light bulb could trigger the short
i plan to swap out the gauge cluster to see what happens

[dlb]

i plan to swap out the gauge cluster to see what happens

that was going to be my suggestion, assuming you had a spare kicking around.

[xirdneh]

swapping the gauge cluster took care of it

[irowiki]

You can swap just the temp part if you want to save your odometer etc.

[Mark]

My previous car ('84 Camry) had the same problem. When I pounded my fist on the dashboard the temp gauge needle would often drop back down to normal for awhile so I guess temp gauges do go bad.

[marlinh]

I also have had several of cars do this. Tap on the front of the gauge and it drops to normal.

[irowiki]

This sort of tapping?

[marlinh]

Slight overkill Paul, ha ha.