I have a 99 CTD and for some reason, I can't get my heater to blow hot air. I have no leaks from the core, but the fan no longer blows as hard as it once did. The truck is getting up to normal operating temps and the tstat is opening. For some reaon though, the heater will only blow luke warm air. It is the same temp no matter what position the selector is on. The AC still works fine, and all locations are working well. My only problem is the temperature of the air coming out when I have selected the hottest setting. Any takers? Thanks

 

...never had that issue, but it sounds as though your temp adjustment **** isn't working correctly? You can pull the dash face real easily, and pull the rotary **** assembly out, give it the eyeball, see if anything obvious is wrong...check for throw (I'm not sure if this operates a mechanical linkage to the coolant flow to the heater core?); Or....perhaps your lines are plugged (vapor lock?) and you're not flowing hot fluid to the h. core....

 

Another thought...

You might pull the fan out and check the blower. I've seen them pack up with debris and leaves. You might have to reach up inside and clean it out too... Things like cootonwoods will do these things...