Not dialed in on dash air problems and I have one.
My defrost blows 100mph with a lot of volume but the dash air and floor air trickles out. Anyone have an idea about a likely cause of that issue?
Tommy in your Foretravel book it will have a diagram on how the system operates. Vacuum pump powered control valves. Probably have a disconnected line and the system has defaulted to defrost for safety, not comfort. Have to get into your coach book and figure it out. They may all be the same or different. I wouldn't know. When operating you can hear the doors popping open and close with changing air noise and flow.
Scott
Thanks Scott, Dash air works as does the defrost when selected by the knob but the the volume of air pushed out when defrost is selected is far greater than any other selection.
Tommy, Would like to know what you find. I am having the very same issue with our (new to us) 01 U295. I have the dash completely removed, but have yet to dive in. and find all the vacuum control valves and source of vacuum. Getting with previous owner they say it was that way entire time they owned it. Time to fix, deep south summers too darn hot for just defrost mode.
UPDATE***** Found mine to be the vacuum pump located behind the door step. Appears the old pump had obviously failed long ago and had been left in place and a newer Ford/Hella pump placed next to it.. The Ford pump had a bottom plate that was easily pulled off and access to the pump itself was possible. The egg shaped cam that helped generate vacuum had a small amount of oxidation on it that would not allow it to rotate. I few light taps and some sewing machine oil on the cam and were back in business.
Good recent topic on the subject How Dash Air Works - U320 (https://www.foreforums.com/index.php?topic=41410.0)
Dash air on my 2000 is same. When selecting from dash to floor, I hear the door close/open, air stops at dash vents and comes out floor vents. Works same when switching from floor to dash. But when switching to defrost, its like I turned the fan on high. Much more air volume and fan noise. I have not looked into this but now may be the time.
Newer systems are electric valves, older system they were operated by vacuum
When on floor or dash, no air coming out of defrost?