I have a 98 f150, I'm trying to figure out why I have no heat. I first checked to see if coolant was circulating through my heater core. I found the inlet line and felt that it was warm and getting hotter, a few minutes later felt the outlet line and it to was getting warmer, so I figured that it is circulating properly. I then checked to see if the actuator for the blend door was working, and it was also. So then I opened up the air box, behind the glove compartment and saw that the door is actually moving the way it's supposed to. Still no heat. Any suggestions on what else it could be? Not sure if this would effect it, but a few months ago I did have to remove my a/c compressor because the bearing seized up. I had to remove it and only left the accumulator and condenser. Would this also cause the heater not to work?

 

The defroster will not be as effective without the AC but the heat should work. going to throw some ideas out, please don't get mad if you have checked these.
Is the blower motor running? You said you checked the blend door, Is the selector door working (select floor, defroster, and vent)? Is the vacuum line for the system leaking/plugged?

Hope these help

 

Similar issues myself.. All positions functional... hot one side/ warm on the other at heater core. Blower works... I'll check the temp door behind the glove box. Thanks for the tips.

 

The blend door (temp) is not accessible or viewable without taking the dash out and the plenum apart, the door behind the glove box is the recirc (max air) door, all that does is either recirculate interior air or let in fresh air from outside.

I recall a common issue with the blend doors them selves breaking where the actuator connects, again no way to know without taking the plenum out and that requires removal of the entire dash assembly.
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Yep... was checking that out this afternoon. Thanks for the tips though. Sitting still on lower blower speeds, the air gets fairly warm but not so much on high blow. On cold mornings it just doesn't get warm.. I'd think it was a thermostat issue but the temp gauge is reading what it normally does and i got it back in the summer.