Home » Public Forums » GMCnet » Dash Heat
| Dash Heat [message #339251] |
Sun, 02 December 2018 16:28  |
SkyKingsley
Messages: 9
Registered: July 2017
Location: Kansas City, MO
Karma: 0
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Junior Member |
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Let's take a poll: how many of you have coaches with the original dash heat in working order? Bought mine without it and haven't missed it but seeing if it's even worth getting it working again. Super involved or easy?
1978 Kingsley -
Kansas City, MO
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| Re: Dash Heat [message #339252 is a reply to message #339251] |
Sun, 02 December 2018 17:09  |
Steve
Messages: 506
Registered: September 2013
Location: East Greenville, Pa
Karma: 1
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Senior Member |
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Like many other coaches, mine had a manual shut off valve under the hood. People install the manual shut off to make sure no heat can get to the cabin during the summer months when you need air conditioning, not heat. I would search for a possible shut off valve. I had my coach out yesterday and the heat was kind of nice.
1978 GMC Royal
Eastern Pennslyvania
1968 Chevrolet C20 396 Camper Special
1969 Chevrolet C20 Camper Special
1985 Buick Electra Park Avenue
1992 Camaro 25th Anniversary Heretage Edition Black
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| Re: Dash Heat [message #339253 is a reply to message #339252] |
Sun, 02 December 2018 17:26 |
tphipps
Messages: 3005
Registered: August 2004
Location: Spanish Fort, AL
Karma: 9
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Senior Member |
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GMC's have a vacuum operated valve in the hot water line to the heater. Being 40 years old, it may have failed. Most have placed a manual valve in this line to keep the hot water out of the heater body to assist in actually getting cooler air when using the A/C.
This is the first place to look.
Om
2012 Phoenix Cruiser model 2552
KA4CSG
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| Re: Dash Heat [message #339262 is a reply to message #339251] |
Sun, 02 December 2018 19:19 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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SkyKingsley wrote on Sun, 02 December 2018 17:28Let's take a poll: how many of you have coaches with the original dash heat in working order? Bought mine without it and haven't missed it but seeing if it's even worth getting it working again. Super involved or easy?
Kingsley,
As a 78, you are supposed to have the final and best HVAC. My 73 is adequate for the situations we have been exposed to, but I added a valve in the heater line anyway. My heater valve had died long before, but I found a replacement. If you replace that valve, be sure that you know what you are doing because, at least in my 73, that valve was vacuum to CLOSE.
One of the reasons I am sure that it opened as we crossed the Bighorn. It kind of had to, there was no vacuum left.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: [GMCnet] Dash Heat [message #339263 is a reply to message #339251] |
Sun, 02 December 2018 19:27 |
Dolph Santorine
Messages: 1236
Registered: April 2011
Location: Wheeling, WV
Karma: -41
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Senior Member |
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Working.
Easy to fix.
Yes, I use it.
Dolph
DE AD0LF
Wheeling, West Virginia
1977 26’ ex-PalmBeach
Howell EFI & EBL, Reaction Arms, Sullybilt Bags, Manny Transmission
“The Aluminum and Fiberglass Mistress"
> On Dec 2, 2018, at 5:28 PM, Andrew wrote:
>
> Let's take a poll: how many of you have coaches with the original dash heat in working order? Bought mine without it and haven't missed it but seeing
> if it's even worth getting it working again. Super involved or easy?
> --
> 1978 Kingsley -
> Kansas City, MO
>
> _______________________________________________
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| Re: Dash Heat [message #339266 is a reply to message #339251] |
Sun, 02 December 2018 21:43 |
GatsbysCruise
Messages: 261
Registered: January 2017
Location: Waukegan, Illinois
Karma: 3
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Senior Member |
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My 74 Glacier was and hand me down from 3 other po's.
some one along the line disconnected all the vacuum lines to the dash controls, they sealed them by melting them closed.
This stopped any air flow through the dash vent system.
My fix was to prop the vent doors open to allow air flow.
I didn't have heat, neither did the PO before me.
The fix was to replace the cable from the dash control box to the heat/ac box under the hood where it attaches to a vent handle on the right side.
What made mine fail was the heat/ac box vent door was closed to heat, that is air could not flow through to the heat core to heat the air.
The cable attaches by a screw to the heat control in the dash. This attachment is plastic, and mine was broken.
With this broken, you could move the lever to the heat side of the control and only the entire cable moves, not the wire inside which would have moved the lever to move the door on the heat/ac box under the hood.
Once this cable was replaced, the dash blew out hot air.
I have one of those valves under the hood to shut down the hot water to the heater but it turns out with the dash control to from heat to cool, the door closes and there is no hot air infiltration. I never use it.
If it is your cable in trouble, look at how it is attached to the dash heater control, it can be put in back wards and will not work as it will slip and be in operable. It sort of snaps in but if itis broken, itis hard to see this.
EDIT:
If you are not getting HOT air flow from the dash, the first thing to check would be your coolant levels. Low coolant can actually prevent heat from coming from the dash.
GatsbysCruise. \
74GMC260 Former Glacier Model style. \
Waukegan, Illinois \ Keep those MiniDiscs Spinning \ MY GREYHOUND IS FASTER THAN YOUR HONOR ROLL STUDENT \ WindowsXP-Win7-Win8.1-UBUNTU STUDIO - UBUNTU VOYAGER - Berzin Auto Center
[Updated on: Fri, 07 December 2018 08:16] Report message to a moderator |
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| Re: Dash Heat [message #339283 is a reply to message #339251] |
Mon, 03 December 2018 17:27 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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My 77 works great in all modes. Earlier, heat was not great but I have attributed that to air up high in the heater core which has resolved itself. As Matt said water valve on GM is "vacuum to close". This default assures heat, same as loss of vacuum to selector defaults to DEF for safety reasons I use heat position if feet cold but otherwise use VENT to throw warm air further back into the coach. Mine is stock with 100% outside air except on max AC. If you have water flow and a correct 195 stat and your heat temp door works you should have enough heat to satisfy down to zero deg F in cockpit.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Dash Heat [message #339294 is a reply to message #339251] |
Tue, 04 December 2018 09:15 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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Senior Member |
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The dash heat/AC works in my '75. At one point, I broke the plastic pivot pin in the dash heater control, but replaced it with the machined aluminum pin from Alex Sirum (actually purchased from Applied). In the process of replacing that pin, I cleaned and lubricated the control and it has worked properly ever since.
A few years ago, we were heading south from Las Vegas in January on a particularly cold and wet day, and the heat would not work at all, no matter what I did. I have since back-flushed the heater core with a garden hose, and the last time I needed the heat it was working again.
A word of caution about manual ball valves in the heater hose, if left closed all the time, the stagnant coolant will eventually rot out your heater core. I'm guessing that is why the original heat control valve was closed under vacuum, so that it didn't sit in a closed position while not in use.
There are many vacuum lines in that system and any one of them can have small leaks which will prevent proper operation of the system. Check them all.
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member
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| Re: [GMCnet] Dash Heat [message #339296 is a reply to message #339294] |
Tue, 04 December 2018 10:09 |
powwerjon
Messages: 849
Registered: March 2013
Karma: -2
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Senior Member |
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When we purchased our 77 Eleganza II in 1998 we went thru and completely refurbished the HVAC system (type 2). The type 2 system was the upgraded and redesigned system to fix all the past evils of the past HVAC systems used in the GMC. We replaced the following items, compressor, AC hoses, all heater hoses and misc parts of the AC side of the system and charged the system with R12 which was still available. The radiator was recored with he HD core and the evaporator and condenser were flushed before reassembly vacuum checked before being charged. The HVAC would frost my knees and legs with its output and would cool the entire coach even on a HOT day. The system was rated at 3 tons cool capacity which was the same as the capacity of my home that I had in Louisiana. That system worked great until we sold the coach in 2011. Will be rebuilding the stretch HVAC also a type 2 system, this coming spring to try an achieve the same level of performance. We will be using Duracool as the refrigerant.
JR Wright
Michigan
On location in Tucson
> On Dec 4, 2018, at 8:15 AM, Carl Stouffer wrote:
>
> The dash heat/AC works in my '75. At one point, I broke the plastic pivot pin in the dash heater control, but replaced it with the machined aluminum
> pin from Alex Sirum (actually purchased from Applied). In the process of replacing that pin, I cleaned and lubricated the control and it has worked
> properly ever since.
>
> A few years ago, we were heading south from Las Vegas in January on a particularly cold and wet day, and the heat would not work at all, no matter
> what I did. I have since back-flushed the heater core with a garden hose, and the last time I needed the heat it was working again.
>
> A word of caution about manual ball valves in the heater hose, if left closed all the time, the stagnant coolant will eventually rot out your heater
> core. I'm guessing that is why the original heat control valve was closed under vacuum, so that it didn't sit in a closed position while not in use.
>
> There are many vacuum lines in that system and any one of them can have small leaks which will prevent proper operation of the system. Check them
> all.
> --
> Carl Stouffer
> '75 ex Palm Beach
> Tucson, AZ.
> Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles,
> Solar battery charging. GMCSJ and GMCMI member
>
> _______________________________________________
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> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
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| Re: [GMCnet] Dash Heat [message #339303 is a reply to message #339302] |
Tue, 04 December 2018 15:08 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Senior Member |
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The restriction was put there to keep the heater coil from making noise as
fluid flows.
On Tue, Dec 4, 2018 at 11:41 AM Emery Stora via Gmclist <
gmclist@list.gmcnet.org> wrote:
> There is a 15/64" restrictor hole in the fitting going back into the top
> right rear of the intake manifold. This is where the 5/8" hoses from the
> heater core and the hot water heater loop lead.
>
> Emery Stora
> 77 Kingsley
> Frederick, CO
>
>> On Dec 4, 2018, at 11:37 AM, Larry wrote:
>>
>> For the dash and house water heater, the flow is restricted. Anyone know
> what size hole is in the in-line plug going to the dash heater and the house
>> water heater?
>> TIA
>> --
>> Larry
>> 78 Royale w/500 Caddy
>> Menomonie, WI.
>>
>
>
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--
Jim Kanomata
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: Dash Heat [message #339305 is a reply to message #339251] |
Tue, 04 December 2018 18:38 |
SkyKingsley
Messages: 9
Registered: July 2017
Location: Kansas City, MO
Karma: 0
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Junior Member |
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Hey all, thank you very much for the replies they were super helpful. Turns out there was a bypass installed but it was junk so I replaced it with a new one from home depot. Next I noticed the PO removed the heater temperature valve that is immediately after the HVAC box. Ordered a new one should be able to put it on this weekend.
Next question... When I turn on the valve and try and run the heat, am I going to screw something up? I'm not at all sure the condition of the heater core or how much decades old coolant is hanging out in there. Risky move or no?
1978 Kingsley -
Kansas City, MO
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| Re: [GMCnet] Dash Heat [message #339308 is a reply to message #339305] |
Tue, 04 December 2018 19:53 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Senior Member |
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Should the core leak, just disconnect the hoses and get an reducer and
connect the two hoses.
On Tue, Dec 4, 2018 at 4:53 PM Andrew wrote:
> Hey all, thank you very much for the replies they were super helpful.
> Turns out there was a bypass installed but it was junk so I replaced it
> with a
> new one from home depot. Next I noticed the PO removed the heater
> temperature valve that is immediately after the HVAC box. Ordered a new one
> should
> be able to put it on this weekend.
>
> Next question... When I turn on the valve and try and run the heat, am I
> going to screw something up? I'm not at all sure the condition of the heater
> core or how much decades old coolant is hanging out in there. Risky move
> or no?
> --
> 1978 Kingsley -
> Kansas City, MO
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Jim Kanomata
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: Dash Heat [message #339358 is a reply to message #339251] |
Thu, 06 December 2018 15:18 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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You may "knock something loose" in the core but of it fails it was ready to fail anyway. System is pressurized and closing "send " off still presssurizes the core with system pressure, like air in a balloon presses equally in all directions. If heat still poor you can disconnect the heater hoses and backflush with garden hose. Just be careful as tap pressure is like 55-65 and system is 9psi so start slowly until you have good flow to limit pressure rise.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] Dash Heat [message #339359 is a reply to message #339358] |
Thu, 06 December 2018 19:47 |
Dave Stragand
Messages: 307
Registered: October 2017
Karma: 0
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Senior Member |
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For what it's worth, I did a test in my 1978 Transmode on Tuesday. I
turned on the engine, and within a couple of minutes I had warm air. In
10 minutes with the fan on high, the temperature in the midsection went
from 30 degrees to 52. Hope that helps.
-Dave
1978 Transmode near Pittsburgh
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1978 Transmode (403)
Pittsburgh, PA
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