I have an 01 Duallie with a wierd problem maybe one of you can guess the problem.

My trucks blower is stuck in the defrost position. I can not switch to any other positions, like ac. The heat and ac work great, but I just cant get the switch to make it switch from defrost to any other settings. I dont know if it is the switch or of another problem under the dash. I know its air activated, but Im confussed??

Any help would be greatlly appreciated!

 

Sounds like you have lost the vacuum supply. Look up at the firewall drivers side, the vacuum line gets pulled off easily, if not there under the battery box the acid rots the hose away.

 

You are correct that it is vacuum controlled. It could be as simple as the fitting coming off the Actuator down on the floor (to the right of the accelerator pedal, close to the firewall) I believe it is a Yellow line. If that is secure, I would trace the vacuum line from the power steering, across the top of the firewall and back where it goes through the firewall (near the PCM).

I had the line that is near the PCM melt and collapse on itself. This caused a closure and so I was getting no vacuum to my defrost, floor, etc control.