hi all i have a 1999 ford f150 with a 4.2 v6 the heater blows cold if you drive it for about 40 to 50 miles it will start blows hot i have tryed every thing on it i just got this truck in feb. i text the Heater Core the littie Hoses where hot thank you have a nice day

 

Chances are your blend door is broken, or the actuator motor is shot.

Here's a thread that might help - https://www.f150online.com/forums/19...lend-door.html

Andy

 

thank you