Help!!!!

[yellow jacket]

I am on the road and having a problem with the heater. I can't turn the temp down -- heat keeps coming out of the vents --- it feels like its on high . . can't turn on my air -- its unbearable. I'm driving with the windows open. there sounds a soft thumping in the dash. could this be a prob with a gauge??? stuck or maybe a fuse?? any help appreciated asap.

thanx

yellow jacket

 

[fox]

This is just a question mixed with a guess.

Does the 03 trucks use a vacuum pump? If so it may have blown a hose.

If it has the vacuum pump, it should be at the drivers side lower front on the Cummins.

 

[Prairie Dog]

It was common for the heater plenum doors to be broken during assy - Maybe it's something similar?