I live in Northern Pennsylvania, about 9 or 10 degrees last night, so I had the heater on full blast as I was driving down the road, well all of a sudden I start to smell a strange odor and my first thought was "hope that's just the car in front of me and not my heater crapping out." Well, the heater continued to produce hot air and the smell eventually went away, so I figured I lucked out and shut off my truck to hang with friends at a bar. About four to five hours later I come out to start up my truck and absolutely no warmth coming out of the heater, I don't even hear it trying to "blow" the air out. So what does this sound like; a bad heater core, bad blower/fan, the entire heating system needs replaced, bad fuse? Any help would be appreciated.