Temp sending unit

What will cause a temp sending unit to read HOT all the time? It did it a few months ago and I put in a new one and all was fine until yesterday. We were at the hunting land and the truck had been parked for a couple hours. When I get in to go home the temp is pegged out even though the truck is cool. I let it set overnight and this morning the same thing. Could I have gotten a bad one? And what can cause this to go out? I have no leaks and I know that its not running hot.

Where did you get your replacement at? I had to get 3 before mine was right.

My local Ford Stealership

Take it back to ford.

Thats what im going to do first thing in the morning.