Good Sam Club Open Roads Forum: Class A Motorhomes: Windshield defroster question
Open Roads Forum Already a member? Login here.   If not, Register Today!  |  Help

Newest  |  Active  |  Popular  |  RVing FAQ Forum Rules  |  Forum Posting Help and Support  |  Contact  

Search:   Advanced Search

Search only in Class A Motorhomes

Open Roads Forum  >  Class A Motorhomes  >  All

 > Windshield defroster question

Reply to Topic  |  Subscribe  |  Print Topic  |  Post New Topic  | 
atsrmf

Indio

Full Member

Joined: 12/02/2017

View Profile


Offline
Posted: 11/27/20 08:21am Link  |  Quote  |  Print  |  Notify Moderator

I have an older 1987 Class A Gulfstream motorhome that I have restored over the last 3 years. It was in excellent condition to begin with.
There is one nagging problem that I cannot figure out, and that is how does the defroster work?
I cannot divert air to just the defroster like a car, where all the air from the blower comes out the defroster vents. I have examined all of the duct work and have had the dash apart. There doesn't seem to be a diverter door anywhere or a vacuum motor to actuate such a door. Manually closing all of the dash vents does nothing. Is there a vacuum motor inside the plenum somewhere?
The original control head was junk and I replaced it with custom rocker switches that open/close individual vacuum switches for MAX, A/C, and HEAT, and it works great. Getting air to blast out of the defroster remains a setback. There are no leaks at the vents that would allow air to escape under the dash. I'm stumped!
If anyone can find a link to the HVAC vacuum diagram for this would certainly help. There has to be a 4th vacuum motor somewhere.

* This post was edited 11/27/20 08:59am by atsrmf *

enblethen

Moses Lake, WA

Senior Member

Joined: 01/05/2005

View Profile






Posted: 11/27/20 09:09am Link  |  Quote  |  Print  |  Notify Moderator

There should be a vacuum line to operate the mix door which could be inside the heater box assembly.


Bud
USAF Retired
Pace Arrow

2003 Chev Ice Road Tracker


winnietrey

seattle

Senior Member

Joined: 03/26/2005

View Profile



Posted: 11/27/20 09:38am Link  |  Quote  |  Print  |  Notify Moderator

enblethen wrote:

There should be a vacuum line to operate the mix door which could be inside the heater box assembly.


From my experience rats tend to enjoy those vacuum lines as a tasty treat. I wonder if the PO may have had that happen prior to your ownership

atsrmf

Indio

Full Member

Joined: 12/02/2017

View Profile


Offline
Posted: 11/27/20 09:42am Link  |  Quote  |  Print  |  Notify Moderator

I replaced every rubber and vacuum line in the motorhome, including on the engine vacuum lines, cruise vacuum, radiator hoses, heater hoses, and washer hose. I know how age and rodents can cause leaks and problems.
After reading your prior post I went out to the motorhome and exposed the two inside vacuum motors. Both worked perfectly with the engine running. Baffled, I turned off all the vacuum motors and left the fan on. I checked the defroster and air was coming out as designed! Apparently the defrost is the default function when everything is off, the fan just moves more air. The air got hotter as the engine warmed up, so now I understand the factory settings. I never had a manual.
Now I feel like an idiot, but on the flip side I was always convinced that nothing was wrong with the HVAC system. I had tried all the function combinations thinking it would work like a car. Having everything "OFF" never occurred to me.
Now I can drive where it gets cold, something I had been avoiding without defrosters.

* This post was edited 11/27/20 09:50am by atsrmf *

enblethen

Moses Lake, WA

Senior Member

Joined: 01/05/2005

View Profile






Posted: 11/27/20 09:55am Link  |  Quote  |  Print  |  Notify Moderator

Not sure if you changed the flexible air ducts, newer style do not collapse like the old ones.

sch911

Rochester Hills, MI

Senior Member

Joined: 04/13/2003

View Profile



Good Sam RV Club Member


Posted: 11/27/20 10:12am Link  |  Quote  |  Print  |  Notify Moderator

The system when working properly would default to Defrost mode when there is no vacuum present. This is done in all systems to make sure they fail in defrost mode if vacuum is lost during operation. A safety measure. So did you somehow bypass this ability when you re-worked the control head switches?


OEM Auto Engineer- Embedded Software Team
09 Holiday Rambler Endeavor 41SKQ Cummins ISL
2007 Jeep Grand Cherokee Limited Toad


atsrmf

Indio

Full Member

Joined: 12/02/2017

View Profile


Offline
Posted: 11/27/20 01:56pm Link  |  Quote  |  Print  |  Notify Moderator

No, I didn't bypass anything. I was just dumb enough to not figure out what you just stated, which is true.
The duct work is all good, like new, even though it is original.

wa8yxm

Wherever I happen to park

Senior Member

Joined: 07/04/2006

View Profile


Offline
Posted: 11/27/20 04:11pm Link  |  Quote  |  Print  |  Notify Moderator

If there is no vaccum the unit is supposed to default to DEFROST. now if it's an older rig. door may be stuck. In any position. beyond that I can not assist.


Home is where I park it.
2005 Damon Intruder 377 Alas declared a total loss
after a semi "nicked" it. Still have the radios
Kenwood TS-2000, ICOM ID-5100, ID-51A+2, ID-880 REF030C most times


atsrmf

Indio

Full Member

Joined: 12/02/2017

View Profile


Offline
Posted: 11/27/20 04:19pm Link  |  Quote  |  Print  |  Notify Moderator

Vacuum is good, I just didn't understand how the system was designed to work. Now I know.

Reply to Topic  |  Subscribe  |  Print Topic  |  Post New Topic  | 

Open Roads Forum  >  Class A Motorhomes  >  All

 > Windshield defroster question
Search:   Advanced Search

Search only in Class A Motorhomes


New posts No new posts
Closed, new posts Closed, no new posts
Moved, new posts Moved, no new posts

Adjust text size:




© 2021 CWI, Inc. © 2021 Good Sam Enterprises, LLC. All Rights Reserved.