My father has a '99 F150. The AC works, no problem... but the heat doesn't. When you turn the heat on, the fan and everything kicks on, but it doesn't get hot. He's checked and checked, and he's normally pretty good at solving his own problems, especially when it comes to cars/trucks/bikes/anything mechanical. So I'm going to assume it's something small and stupid he may have overlooked.... maybe a censor or something that's not kicking on?

Anyone know F150's that can help?

His next option is to take it to a mechanic, and that can get expensive.

 

Not sure about that one? But I would start with the heater core and make sure the door is open when heater is on.

 

He said he can find two that are working, hear a third, but knows there's a forth. Where?

 

there is a electric servo on the bottom of the heater box that actuates the heat. it often goes bad on 97-03 f150s. its a white box bolted to the bottom of the box in the center near the floor.