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Dash air circulation

I'm having a number of issues regarding the dash air circulation that have been present since I bought the coach this summer:
1- I get good air volume from the defroster, but not from any of the dash vents.
2- If I want to use the dash heater, I have to use the defroster - no warm air from other vents.
3- My dash temp. switch doesn't seem to have any stops.  I can turn the knob around, not knowing what is hot  or cold.  There is some resistance in part of the arc, but I have no idea of what the significance is.
Before I start inspecting every part of this system, has anyone encountered these problems or have any idea if they are separate issues or related?  I would like to know where to start.  I do get cold air through the dash vents, but in low volumes (speed).
I'm guessing that a number of the switches will need replacement.
2000 U320 mid entry  #5688
2006 Jeep Liberty


USMCR retired
SDFD retired
FEMA US&R TF8

Re: Dash air circulation

Reply #1 –
Sven, when you say the switch does not seem to have any stops- are you sure the little set screw in it is tight as it should lock on a flat spot on the shaft coming out of dash. If it is tight and DOES control the shaft then I guess the switch is bad??
JohnH
Coachless, now use aircraft. 2003 Ford Travelair TC280 class C. Super shape. Just for 1 yr .
1994 Ford E350 ClassC,total renovation inside and out. Now sold.
2000 U295  36' Cummins 350 c/w Banks Stinger, Resonator upgrade,Solar, LED lites.Residential fridge with slide out pantry. Build 5674. Sold
ex 92 GV 022C ored Cummins. Sold
ex 95 GV240 cat 3116. Sold
2017 Mini cooper s & 2016 land Rover LR2 HSE  LUX.
jhaygarth@aol.com    SKP #130098
treat everyone as you would like to be.

Re: Dash air circulation

Reply #2 –
John, the set screw is tight. 
2000 U320 mid entry  #5688
2006 Jeep Liberty


USMCR retired
SDFD retired
FEMA US&R TF8

Re: Dash air circulation

Reply #3 –
post a picture of the register(controller) front as seen in the dash, chances are it was a big 3 item.
1988  40' Grand Villa Cat 3208t

Re: Dash air circulation

Reply #4 –
Air only out the defrost vents indicates the "default position"-- the one in absence of vacuum to operate the air distribution system.

So start by verifying that the vacuum pump (front of coach) is working.  If so, verify that you do have vacuum past the vacuum reservoir and to the dash HVAC control. 

Basically, find why you don't have vacuum.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Dash air circulation

Reply #5 –
Quote from: wolfe10 –
Air only out the defrost vents indicates the "default position"-- the one in absence of vacuum to operate the air distribution system.

So start by verifying that the vacuum pump (front of coach) is working.  If so, verify that you do have vacuum past the vacuum reservoir and to the dash HVAC control. 

Basically, find why you don't have vacuum.
I'm getting air out of all vents, but only the defrost vent has high volume (force).  The other vents seem like they are on the low fan setting.
2000 U320 mid entry  #5688
2006 Jeep Liberty


USMCR retired
SDFD retired
FEMA US&R TF8

Re: Dash air circulation

Reply #6 –
I read Jerry Whiteaker's article on Dash Air in the Beamalarm tech section where he described the diverter doors in the plenum as being electrically actuated by small motors.  I thought the vacuum  system did this; if not, what purpose does the vacuum system have?  I  pulled one of the hoses and could not detect much of a vacuum.
I found the problem regarding the switch not having stops (back side of switch rotated).  I'm left with low volume out of all the dash vents and none out of the floor - the dash switch doesn't seem to redirect air movement from one to the other. 
I also saw part of a Bosch motor - for the vacuum or windshield wipers?

2000 U320 mid entry  #5688
2006 Jeep Liberty


USMCR retired
SDFD retired
FEMA US&R TF8

Re: Dash air circulation

Reply #7 –
Sven, I had the same issue with not being able to direct air/heat flow. Turned out no vacuum. I wired in a hot toggle switch and then had vacuum being created, and the Ford dash push button controls worked like they were supposed to.
Can't find the factor vacuum control, tho.
Nitehawk,  Demolition Lady, & our NEW master, Zippy the speeding BB cat.
1989 Grand Villa 36' ORED
Oshkosh chassis, 8.2 DD V8
2006 Saturn Vue AWD

Re: Dash air circulation

Reply #8 –
Sven, Jerrys Whitakers article describes a '96 U270 which contains a integral HVAC unit that is controlled by servo motors. According to the attached document though, it was used thru 1999 model year. Yours may be different. this would be located under the center dash area. I dont know if FT changed to vacuum control in the 2000 model year can someone confirm?
Rick and Wendy Green
1998 U270 3600 The Coach Formerly known as Princess
Build# 5336
2007 Ford Explorer

Re: Dash air circulation

Reply #9 –
I was aware of his coach being an earlier model, but he still had vacuum lines.  What is the purpose the vacuum lines if not for operating the diverter doors?
2000 U320 mid entry  #5688
2006 Jeep Liberty


USMCR retired
SDFD retired
FEMA US&R TF8

Re: Dash air circulation

Reply #10 –
I believe it is the difference between models as much as the different years. Our 99' U270 as electrically actuated flapper motors and only has driver's side controls. I think that the U295's and U320's with the additional passenger side HVAC controls utilize the vacuum motors because of the additional zone. There is no vacuum controls (or vacuum generator) in the dash area of our coach.
Don
Quote from: Sven and Kristi –
I was aware of his coach being an earlier model, but he still had vacuum lines.  What is the purpose the vacuum lines if not for operating the diverter doors?

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Don & Tys
1999 U270 3602 WTFE #5402
Xtreme Stage 1 w/Headlight, Step Conversion, etc.
2009 Honda Fit Sport with Navi
Freedom is NOT "just another word for nothing left to lose"... with apologies to Kris Kristofferson

Re: Dash air circulation

Reply #11 –
Problem solved.  I replaced the three two pole relays on the boost solenoid/battery isolator panel and now I have full air flow out of the dash.  The contacts were pretty corroded back there in the engine compartment.
2000 U320 mid entry  #5688
2006 Jeep Liberty


USMCR retired
SDFD retired
FEMA US&R TF8