Here is a new one for you on my 06' Hemi 1500. Despite having my truck plugged in (oil pan heater and engine block heater) for about 4 hours before going out today and letting my truck idle for about 5 minutes before going out, after 10 minutes of driving on the highway i noticed that the temp gauge had not moved. Everything else looked fine. Turned the heat on and it blew hot air. Then the other odd thing was the electric fan on the A/C condensor behind the grille was running the whole time even when i turned the heat off. I pulled into a parking lot and cycled the heat and A/C between on and off and the condensor fan stayed on. Temperature gauge still at zero.

I shut the truck off, waited a minute then restarted it. The temperature gauge immediatley went up the normap position and the A/C condensor fan was off. The issue never happened again today on all my errands.

Any ideas? I have no idiot lights on the dash and the truck runs fine.