My temp gauge would always go hard over to hot after running for about one min. I change the temp sending unit and now it stays on cold even after driving it. Does any one know what could be wrong?

 

Just because you replaced a part does not mean 1) that the original part was bad or 2) that the replacement part is good.

Otherwise, insufficient information provided.

 

The truck is not over heating and runs fine. I'm just trying to get the gauge to work properly. If you don't know what could be wrong or give suggestions to check, then you shouldn't reply with your useless comments. LOL

 

You just bit the hand that feeds you. Not a good way to get good help.