Greetings!
I'm new here. Subject is a 2005 E450 chassis mini MH. The hvac works okay till engine warms up, then warm air comes out of the vents no matter where the hvac controls set. Leads me to believe that outside air is routed through the heater core. Suspect vacuum leak or vacuum motor quit working. All help to this old timer appreciated.


hilcntry

 

Welcome to site, many possibilities, but have you confirmed the compressor has/ hasn't dropped out when it blows warm?

 

welcome on a board !!

 

Greetings!


No, the compressor hasn't dropped out. For example on a 75% day and a/c off, just trying to bring outside air in with the vents, air coming out of the vents much warmer that outside temp.