Here is my situation. 4.8l v6. 2008. Truck has no issues as long as the outside temp is about about 75*. Once temps go below that I have problems. I leave to go to work and truck has sat all night. Once I drive about 7 miles the temp guage goes from normal to nothing and my A/C wont work. If I disconnect the battery the guage goes back to normal and the A/C works fine until the next morning. Also if I don't disconnect the battery I can get on the highway on the way home and it will start working within 100 yards of the same place every day. I have no problems in the summer, but on the coldest days after sitting all weekend it shows engine hot. It has got to be something to do with the ambient temp.