Love this truck! Traded an F150 for the Hemi Big Horn. Anyway, the problem: Driving to work this morning I had the heat on and it started getting a little warm so I moved the heat selector back some. Didn't help. Turned on AC and still got hot air coming from vents. Only way to stop it was to turn off the fan completely. When I got to work, I turned off the engine and restarted. Turned the AC on and hear the usual vacuum hiss and it seemed to work fine. Anyone have this problem or know what the cause might be???