my jeep likes to do this when im idleing after a long drive or when im at micky ds... within 4 minutes it spikes right up to 250 did it to me twice little stumped on the prob but i prob will change the temp sensor

 

I put a voltmeter on the terminal that connects to the gauge and tested at the firewall, checked out good. Next I tested it from the terminal to the plug in socket behind the instrument cluster pin no 11 and it tested good, that tells me that the line is not broken. Also when grounding the terminal to the block, nothing happens at the gauge. I heard to test it with a load such as a light probe. Didn't get a chance to because the jeep went back to Moab with my daughter. Hate to get whipped but what you going to do? If any of you experts out there have any suggestions, I'ld be grateful. Thanks