Its my dads truck. 2002 ford f150 a/t, 4.6L. The heater core went out so we pulled the dash and replaced it. which sucked by the way!! Now to the problem.

The truck had working heat for a while after the core was replaced but now that seems to have gone away. The blower motor control when selected for floor heat puts out heat but when changed to anything else it sounds as if the a/c clutch engages and the heat cools off. It isnt cold air but is no longer hot? any help?

 

do some more chekcing. the heater dont work that way... where the air comes out is vacuum controlled. how hot the air comes out is controlled by the **** and electric motor. read this

https://www.ford-trucks.com/forums/9...h-a-twist.html