| Dash Air Control Panel [message #239003] |
Thu, 06 February 2014 16:33  |
djester
Messages: 145
Registered: January 2014
Location: Indianapolis
Karma: 0
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My heater control panel is all screwed up. In "vent" I can get a small amount of heat, but in any other position there is no heat. Also, there is no heat coming out in the driver's feet area.
I read somewhere that the "vacuum select valve" and the "vacuum temp valve" should be lubed, but I'm not sure what that is, or where located, but may be at rear of heater control.
Hate to dive in without knowing what I'm looking for. Anyone have a picture of control out of the dash?
David A. Jester
Indianapolis, In
1975 Palm Beach
djester@comcast.net
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| Re: Dash Air Control Panel [message #239011 is a reply to message #239003] |
Thu, 06 February 2014 16:55  |
djester
Messages: 145
Registered: January 2014
Location: Indianapolis
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Yes, mine has one too, but it is wide open. I'm getting heat, but I can't direct it anywhere, or get heat other than on "vent".
David A. Jester
Indianapolis, In
1975 Palm Beach
djester@comcast.net
[Updated on: Thu, 06 February 2014 16:56] Report message to a moderator |
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| Re: Dash Air Control Panel [message #239015 is a reply to message #239003] |
Thu, 06 February 2014 17:07 |
djester
Messages: 145
Registered: January 2014
Location: Indianapolis
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That's great. I think that shows what I needed to know, namely, the location of the valves.
David A. Jester
Indianapolis, In
1975 Palm Beach
djester@comcast.net
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| Re: [GMCnet] Dash Air Control Panel [message #239020 is a reply to message #239015] |
Thu, 06 February 2014 17:39 |
Bruce Hart
Messages: 1500
Registered: October 2011
Location: La Grange, Wyoming
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David, make sure you have vacuum to the selector, if not the heat will
default to the windshield defroster.
On Thu, Feb 6, 2014 at 4:07 PM, David Jester <djester@comcast.net> wrote:
>
>
> That's great. I think that shows what I needed to know, namely, the
> location of the valves.
> --
> David A. Jester
> _______________________________________________
> GMCnet mailing list
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--
Bruce Hart
1976 Palm Beach
Milliken, Co
GMC=Got More Class
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Bruce Hart
1976 Palm Beach
1977 28' Kingsley
La Grange, Wyoming
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| Re: [GMCnet] Dash Air Control Panel [message #239021 is a reply to message #239020] |
Thu, 06 February 2014 17:46 |
djester
Messages: 145
Registered: January 2014
Location: Indianapolis
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Interesting thought. I just bought this vehicle and have an hour behind the wheel, bringing it home. Don't recall checking to see if getting defroster flow. Thanks.
David A. Jester
Indianapolis, In
1975 Palm Beach
djester@comcast.net
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| Re: [GMCnet] Dash Air Control Panel [message #239027 is a reply to message #239023] |
Thu, 06 February 2014 18:59 |
Otterwan
Messages: 946
Registered: July 2013
Location: Lynnwood (north of Seattl...
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| mikethebike wrote on Thu, 06 February 2014 16:24 |
There is a vacuum check valve inline with the vacuum reservoir, if it fails that might be part of the problem. But, just in case I'd WD-40 the manifold. Couldn't hurt. I installed a heater BYPASS valve in the Royalle instead of a heater shut-off valve and this allowed me to remove the 'y' fittings that were spliced into the heater hose to feed the water heater.
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Why did you remove the "Y"s? I love getting to where I'm going and having a tank of hot water without needed to fire up the propane water heater.
1977 Birchaven, Lynnwood WA - "We may not be able to stop all evil in the world, but I know that how we treat one another is entirely up to us."
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| Re: Dash Air Control Panel [message #239030 is a reply to message #239003] |
Thu, 06 February 2014 20:03 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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| djester wrote on Thu, 06 February 2014 15:33 |
My heater control panel is all screwed up. In "vent" I can get a small amount of heat, but in any other position there is no heat. Also, there is no heat coming out in the driver's feet area.
I read somewhere that the "vacuum select valve" and the "vacuum temp valve" should be lubed, but I'm not sure what that is, or where located, but may be at rear of heater control.
Hate to dive in without knowing what I'm looking for. Anyone have a picture of control out of the dash?
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Although it could be the vacuum "wafer" in the control head, it could also be sticking doors in the HVAC box. This is one of the notorious issues as well. Whenever I think of it, i try to cycle the controls through all of the positions inorder to keep the doors loosened up.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: Dash Air Control Panel [message #239031 is a reply to message #239030] |
Thu, 06 February 2014 20:04 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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| Bob de Kruyff wrote on Thu, 06 February 2014 19:03 |
| djester wrote on Thu, 06 February 2014 15:33 |
My heater control panel is all screwed up. In "vent" I can get a small amount of heat, but in any other position there is no heat. Also, there is no heat coming out in the driver's feet area.
I read somewhere that the "vacuum select valve" and the "vacuum temp valve" should be lubed, but I'm not sure what that is, or where located, but may be at rear of heater control.
Hate to dive in without knowing what I'm looking for. Anyone have a picture of control out of the dash?
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Although it could be the vacuum "wafer" in the control head, it could also be sticking doors in the HVAC box. This is one of the notorious issues as well. Whenever I think of it, i try to cycle the controls through all of the positions inorder to keep the doors loosened up.
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I forgot to mention that if it is due to sticking doors, they will move better if the blower is on low.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: Dash Air Control Panel [message #239040 is a reply to message #239003] |
Thu, 06 February 2014 21:32 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Before ripping into the dash trace the vac supply line to the engine. The hoses under dash ( indoors) are usually still in good shape. The underhood stuff can be hard and cracked. Also the button fastener that pops in to hold the rotary selector wafer together likes to have it's little retainers break off and then it leaks vac. I think Jim K at Applied GMC has them
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Dash Air Control Panel [message #239044 is a reply to message #239040] |
Thu, 06 February 2014 23:08 |
djester
Messages: 145
Registered: January 2014
Location: Indianapolis
Karma: 0
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What's the old saying about being careful what you ask for . . . you guys are talking way over my pay grade in a number of instances. This vehicle is completely and absolutely new to me. What I know about it you could stick in your eye and not feel a thing. 
I'd never touched a wrench until I retired 12 years ago, but since then I've restored a couple of old military vehicles. They are, however, the simplest vehicles ever made. Most repairs can be done in the field, of course. This is an entirely different kind of animal!
I'm going to start through the suggestions and see if I can figure it out. I guess the first question I should start with is: how do you get to the innards of the system? Under the dash or does the dash have to come out?
(of course, after checking the vacuum lines.)
David A. Jester
Indianapolis, In
1975 Palm Beach
djester@comcast.net
[Updated on: Thu, 06 February 2014 23:17] Report message to a moderator |
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| Re: [GMCnet] Dash Air Control Panel [message #239047 is a reply to message #239046] |
Thu, 06 February 2014 23:27 |
djester
Messages: 145
Registered: January 2014
Location: Indianapolis
Karma: 0
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Jim, you are exactly right. A parts manual goes a long way to understanding equipment. Will do.
David A. Jester
Indianapolis, In
1975 Palm Beach
djester@comcast.net
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| Re: [GMCnet] Dash Air Control Panel [message #239058 is a reply to message #239047] |
Fri, 07 February 2014 07:23 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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David,
More important than the parts manual is the service manual(s). You'll find
them all here:
http://www.bdub.net/manuals/index.html
Since you haven't yet begun to use a signature line with your GMC
identification and location, like most of us, I can't tell you which
manuals to download. But basically, if you have an even model year, you'll
need the previous year's manual and a supplement for your year.
Another good reason to list your location is that there may be someone near
you who would be willing to walk you through your coach and give you a
"data dump" -- mentor you, if you will. And alternative is to attend a GMC
club rally and get the same treatment. At GMCMI Conventions, we try to run
a formal Mentoring program.
Welcome to the zoo.
Ken H.
Americus, GA
'76 X-Birchaven w/Cad500/Howell EFI & EBL
www.gmcwipersetc.com
On Fri, Feb 7, 2014 at 12:27 AM, David Jester <djester@comcast.net> wrote:
>
>
> Jim, you are exactly right. A parts manual goes a long way to
> understanding equipment. Will do.
> --
> David A. Jester
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: Dash Air Control Panel [message #239089 is a reply to message #239044] |
Fri, 07 February 2014 12:58 |
A Hamilto
Messages: 4508
Registered: April 2011
Karma: 39
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Senior Member |
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| djester wrote on Thu, 06 February 2014 23:08 |
What's the old saying about being careful what you ask for . . . you guys are talking way over my pay grade in a number of instances. This vehicle is completely and absolutely new to me. What I know about it you could stick in your eye and not feel a thing.
I'd never touched a wrench until I retired 12 years ago, but since then I've restored a couple of old military vehicles. They are, however, the simplest vehicles ever made. Most repairs can be done in the field, of course. This is an entirely different kind of animal!
I'm going to start through the suggestions and see if I can figure it out. I guess the first question I should start with is: how do you get to the innards of the system? Under the dash or does the dash have to come out?
(of course, after checking the vacuum lines.)
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As has been mentioned previously, download the Maintenance Manual from here
http://www.bdub.net/manuals/X7525/X7525.pdf
Then look at page 1-47 for the locations of most of the actuators.
I think the temperature slider on the dash control moves the temperature door inside the blower box, and the far left position engages the water valve actuator (closes to stop coolant to the heater core, opens to allow coolant to the heater core). The way mine works, coolant to the heater core is either full on or full off, and the temp of the air flowing through the system is controlled by the temp door which controls what percentage of air flows over the heater core and what percentage bypasses it.
The rest of the controls are for airflow (vent and ac and heat and defrost) which is done by vacuum actuators opening and closing.
I would first make sure the line to the vacuum tank (page 1-43, figure 15) is not leaking or plugged between it and the engine then check the line between the vacuum tank and the dash control.
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