Airconditioning/heater vent on Class A not closing?

[Serrano4657]

In the summer it gets really hot here in Riverside, Ca about 110 degrees.
We use the roof air when we are traveling. The dash air does not work which is ok but we are always getting hot air from outside when we are going down the road. We move the knob on the air/heater but it does not seem to close the vents. What could be wrong?
???

 

[Will]

You are probably getting hot air from behind the radiator/engine compartment.  Does your A/C control have a recirculate/"Max AC" setting?  Set if to that but leave the fan off so the compressor doesn't click on and see if the wind doesn't stop blowing in the vents.  If you can't set it to recirculate/"max ac" without having the fan turned off then you can reach under the hood and disconnect the wire that goes to the compressor clutch to keep if from engaging.

 

[Gary RV_Wizard]

The vent doors are usually operated by air pressure (vacuum, actually, - they get sucked open or closed), so most likely an air line has come loose from its connector.

 

[Serrano4657]

Let me make it simple, what ever the tempature is out side while driving, thats the tempature that comes in through the dash. The vent will not close. I don't care if it cold outside, but when your driving in 90 degree weather and the roof top air is blowing cold air, its still 90 degrees coming out of the dash vent.

 

[Ron]

This could be caused by a disconnected or leaking vacuume hose.