So the other day it was kind of chilly so I turned on the heat to defrost my windshield on the way to work. After work I go to turn my a/c on and I noticed it was still blowing hot and not cold so I gonto turn my climate **** to hot and back to cold thinking maybe it was hung up and it wouldn't go all the way to hot, like it was stuck. I could turn it harder and it would start to go but would bounce right back. I got to Messing with it and finally got it unstuck but it's still blowing hot with the ac on. The compressor is turning on and off when I turn it to ac to fan. 1997 2500 cummins

 

Temp door is controlled by a cable, likely yours is jammed up somewhere. Trouble is, it's on TOP of the heater box..... so you basically need to pull the dash to see what's up with it.

Welcome to DF!