My dash guage stays at the middle of the "E" after warming up without the radiator fan being connected.After driving today 55* outside temp for 10 miles at 65mph it still didn't go much above the middle of the "E" even after shutting it off.It does go to O when cold and does move to the "E" when warm but no further.I had the head replaced and don't want to have it fail because the guage is faulty.

 

Does the E mean middle of the gauge? If so that is normal. The cooling fan does not operate while on the highway, it is only for stop-and-go city driving. The radiator cools with a "ram air" effect while highway driving. If you are really that concerned about the accuracy of the gauge, go to an auto parts store and get an underdash mechanical unit. It can install in place of the factory sending unit location or you can get a "tee" fitting and hook both up at the same time.