97 f150 4x4, 4.6. so my temp gage suddenly pegs out, disconnected the sensor (the one that goes into the intake manifold) and the gage goes all the way down to cold. went to napa and sourced a new temp sensor, installed it, and no reading on the gage, even after the engine is warm and the heater is cranking. took the sensor back to napa and they gave me another one from a different store, different lot #, and the same result, no reading on the gage. reinstalled the original old one, turned on engine, reads cold, as soon as it heats up a little, goes to full hot. what is going on? am i doing something wrong? two bad sensors in a row seems somewhat problematic. help please. thanks