I had no heat in my '99 F150 and I read a lot of the threads describing the possible causes including a broken blend door, bad actuator, blown fuse, plugged heater core, etc. I checked into each cause only to find out mine was just a cut wiring harness for the actuator. Something was screwed to the bottom of the dash by the original owner and I'm thinking before he traded in the truck, he must have cut the harness when he was removing that something. I'm glad I didn't have to remove the dash to replace the blend door! Anyways, thanks for all the good threads.