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Topic: Dash air problem (Read 531 times) previous topic - next topic - Topic derived from 2001 U320 dash air sw...

Dash air problem

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?

2000 GV320 4010 build #5712  2019-?
1999 Bounder 2000-2008
Bardstown, KY
🥃The Bourbon Capital of the World🥃

Re: Dash air problem

Reply #1 –
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

Re: Dash air problem

Reply #2 –
Quote from: dsd –
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. 

2000 GV320 4010 build #5712  2019-?
1999 Bounder 2000-2008
Bardstown, KY
🥃The Bourbon Capital of the World🥃

Re: Dash air problem

Reply #3 –
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.
Mike in AL
2001 U295
8.3 ISC 350
Build 5918

Re: Dash air problem

Reply #4 –
Good recent topic on the subject How Dash Air Works - U320
Learn every day, but especially from the experiences of others. It's cheaper!  - John C. Bogle

2000 U320 36' non-slide / WildEBeest Rescue
2003 U320

Re: Dash air problem

Reply #5 –
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. 
Bill and Joyce, The House2 and Dashboard Pig III
2000 U320 4210 CAI (The House2)
Build # 5733
2019 F150 King Ranch FX4

Re: Dash air problem

Reply #6 –
Newer systems are electric valves, older system they were operated by vacuum

Quote from: Bill B –
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. 

When on  floor or dash, no air coming out of defrost?
2014 ih45  (4th Foretravel owned)
 1997 36' U295 Sold in 2020, owned for 19 years
  U240 36' Sold to insurance company after melting in garage fire
    33' Foretravel on Dodge Chassis  Sold very long time ago