Crazy Temp Gauge

[The Kid]

Hey Guys,
My temp gauge has been doing some weird things lately. It will all but peg and then come back down to normal for no real reason. It never happens while im sitting and idling, it only does it while im driving. Lastly, if i come to a stoplight and the gauge is acting up and I turn the car off and then put the key back into the on position it will read normal. Any help would be great.

Thanks,
The Kid

 

[StealthWyvern]

temp sensor or t-stat acting up.

 

[Matt V]

I would say it's time to replace the thermostat.