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Topic: Dash air circulation (Read 873 times) previous topic - next topic

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.

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

Re: Dash air circulation

Reply #2 –
John, the set screw is tight. 

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.

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.

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.

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?

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.

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?

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?

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?

 

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.