Dash air conditioning

T

tom geiger

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Dec 31, 2006
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So I’ve been reading some previous postings on new dash air-conditioning compressors. I’ve got the document of the new compressors that will
work. What is not clear with the document is will these compressors work as a direct drop in with the v-belt pulley?, and is the A6 hose manifold
connect to them or is there mods for that? I paid a local mechanic to get my A6 system converted to 134a. He was all about the A6 compressor and
convinced me to keep it. Well it never worked very well so now I want to get the A6 pulled and get a new one in. So as I read I want to flush the
system, add new oil to the system, (not sure what’s entailed on that), get a new dryer installed and air pressure the system to make sure it hold
pressure. Not sure of the sequence of these. Is there other documents I can read that describes the complete conversion process to operation? I’m
understanding the damper conversion process pretty well, it’s just the compressor swap I’m not clear on.

Thanks,
TG
--
Tom Geiger
76 Eleganza II
KCMO
 
Tom,

First off about the already-done conversions from R-12 to R-134A: If the
mechanic did it properly, he did all the flushing, etc., you describe as
possibly needed now. I wouldn't plan to do all that again unless you've
had a compressor failure, possibly polluting the system, since then.

For the "new" system, I strongly recommend one of the hydrocarbon-based
coolants, Freeze-12, Duracool, etc., for several reasons. First off
they're generally cheaper. Second, they cool better than even R-12, and
much better than R-134A. Third, they're compatible with all approved
compressor lubricants (unlike R-134A which required removal of all traces
of the R-12 oil). Fourth, they require less compressor "head pressure" in
operation, reducing the load, and expense of A/C operation and reducing
wear. The concerns expressed by some of putting "flammable propane" in the
cooling system ignore the fact that R-134A is just as flammable when mixed
with its oil, and generates worse combustion products. Besides, when was
the last time you heard of an "air conditioner fire"? :-)

If you can find a GM vehicle (late 90's vans?) with a Sanden-like
compressor, it may have GM compatible connections directly usable with your
existing hoses. Failing that, any good A/C supply shop can adapt 'most
anything to anything with new or modified hoses.

That's been my experience. Now, I need to go out and refill my system with
Duracool. It had run for about 5-6 years without "topping off" but was
beginning to cool less well when the pandemic shut down all interest in it
for 18 months. It's now nearly empty. And I had to order new hoses for my
manifold set; after only 20-30 years, one of them began to leak. :-(

Ken H.

> So I’ve been reading some previous postings on new dash air-conditioning
> compressors. I’ve got the document of the new compressors that will
> work. What is not clear with the document is will these compressors work
> as a direct drop in with the v-belt pulley?, and is the A6 hose manifold
> connect to them or is there mods for that? I paid a local mechanic to get
> my A6 system converted to 134a. He was all about the A6 compressor and
> convinced me to keep it. Well it never worked very well so now I want to
> get the A6 pulled and get a new one in. So as I read I want to flush the
> system, add new oil to the system, (not sure what’s entailed on that), get
> a new dryer installed and air pressure the system to make sure it hold
> pressure. Not sure of the sequence of these. Is there other documents I
> can read that describes the complete conversion process to operation? I’m
> understanding the damper conversion process pretty well, it’s just the
> compressor swap I’m not clear on.
>
> Thanks,
> TG
> --
> Tom Geiger
> 76 Eleganza II
> KCMO
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
 
If you don’t like the performance with the A6 and 134a, keep in mind the Sanden has less BTUs.
--
John Lebetski
Woodstock, IL
77 Eleganza II
 
Biggest issue with the GMC's dash A/C is the design of the airflow. There have been several redesigns of the HVAC box and ducting over the production
years, with the '77 & '78 models having the best operation.

Here is a rally presentation on the GMC HVAC system's over the years and a few improvements you can make.

http://www.gmcws.org/Tech/air_conditioning/air_conditing.html

FYI, I found a good improvement of airflow when the dash vent louvers would no longer stay in place so I removed them while I tried to find better way
to keep them in place. There was a substantial improvement in airflow from the vents without them in place, so they sit in the shop for now! I have
a 1977 with the latest revision in the HVAC system.

--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
 
Thanks guys for getting back. Sorry on the delay, was out mowing the grass before it got to 102 today. Man it felt like it already reached that. Ken
would love to get a compressor from the junkyard because I’m all about recycling and repurposing things if I can. I’m just not confident on
weather it will hold up. See my luck with mechanical things working for me is patchy at best so kinda thinking a new or remanufactured one. Just
have to pick out one that is good and as close to plug and play as possible.

Thanks,
TG
--
Tom Geiger
76 Eleganza II
KCMO
 
I think others have touched on this but I'd like to reiterate that the design of the dash air on a 1976 GMC motorhome is poor from the start. The
compressor is not likely the problem, unless you have leaks, bad bearings, etc. The A6 is a fairly large displacement compressor (I think), and is
very durable.
There are modifications (I have not yet tried) that improve the air flow through the system. Air flow is what is lacking in our systems, I believe,
and the mod in this link looks like a good fix.
http://www.gmcmhphotos.com/photos/g4637-type-ii-dash-air-condition-modification.html
http://www.gmcmhphotos.com/photos/g4637-type-ii-dash-air-condition-modification.html

Alternately people have installed a second evaporator, as the compressor and condensor are sufficiently sized, to augment the dash air. Some install
these under the dash, the sofa, passenger seat, one even repurposed a rear unit from an old Chevy Suburban to the roof in the rear.
https://www.vintageair.com/builder-series/
https://www.vintageair.com/builder-series/
So my guess is that your compressor is not the culprit. All other suggestions have been good too.

Good luck and please keep us posted on your progress.
--
Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, Ca
Howell EFI + EBL + Electronic Dizzy
 
Tom-

the changing of a compressor to the Sanden, is something I would do. Yes it is less BTU's, but it has plenty enough unless you are adding large
multiple evaporators. It does not seem to load the engine like the A-6. I cannot ever tell when the compressor clutch kicks in or out, is runing or
not running.

the conversion is always more complicated then some make it sound, but it is not anymore complicated then probably anything else you can do.

you need the compressor itself, and it uses a different bracket. the compressor comes with a 2 grove V belt pully, and you need a different belt for
it. you will not need 2 belts, one of the two grooves lines up properly.
(napa XL-7585 is the one I am using).

the hose fittings to the compressor are completely different, then what the A-6 uses. so you either need new hoses made, or if your hoses are in
good shape, you maybe able to cut of the old fitting and crimp on a new one.(I have not done or tried this). Jim K's kit I think comes with the
needed hoses. You also have to cut and wire up the wire that engages the clutch, as that connector is different between the compressors.

If yours is converted to r-134, you should be fine on refrigerants as long as you don't install another compressor with the old oil in it. as I
understand the oil is what you don't want to mix.

I installed the new compressor/bracket/belt, made my own hoses and have them up to a vintage air under dash aux. evaporator, bypassing and not even
using the original dash air evaporator. I replaced the dryer, and I used a aerosol "flush" can and compressed air to blast everything out of the
condensor(the only part that I retained from the OEM system). so I am running PAG oil now with duracool refridgerant.

--
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
 
Thanks Jon, will take note on your info here. Is the climate vacuum control stuff I need to check thru as well. I’m reading some concerning post on
leaky vacuum systems. Wasn’t there a electronic control system available. Heck I’m even considering old choke type cables to control the
dampener doors even as someone did on theirs.

TG
--
Tom Geiger
76 Eleganza II
KCMO
 
Just troubleshoot your vac leaks and repair. It’s all there and it worked, not hard to get it to work again compared to reengineering. You should
have that max air duct on a 76. Not as good as 77-78 but second best. Problem may be underhood with miss patched vac lines. Second place to check is
the broken nylon pin on selector matrix wafer. Sirum has them in metal.
--
John Lebetski
Woodstock, IL
77 Eleganza II
 
What should the high and low pressure be when using duracool?
--
1977 Kingsley 455 as stock as it gets except lots of Ragusa parts
 
Hi Mike,

I think the pressures are much less than the 134a system which is in the 120-130 range if I remember correct. Duracool operates down in the 30# range.
I’ll let others here answer this more accurately. Here below is a link that has a ton of information on its installation and use.

https://www.duracool.com/Duracool/faqs.html

TG
--
Tom Geiger
76 Eleganza II
KCMO
 
So beyond the compressor change it sounds like I need to do some duct modifications to make my system cool better. I’ve read that the modification
moderately improve the cooling. I did see someone’s posting about adding his own separate routing of air con venting that had vents on the
floorboard of the driver and passenger side. Just was wondering on that kind of mode worth it? If not, all good, I can just make the ductile modes
and put it back together. If I dig into this I’m just trying to get the best end result.

Thanks,
TG
--
Tom Geiger
76 Eleganza II
KCMO
 
Every time I hear someone mention added ductwork I remember John & Linda
Richardson's battery fire a few years ago: The batteries somehow caught
fire, causing a raging inferno under the right front hood. Someone had
added a duct which entered the cockpit just above Linda's feet. The flames
immediately burned through the duct, passed behind the dash and over her
head, then followed the roof toward the rear. They got out unharmed,
somehow, but despite a firetruck being nearby and putting the fire out
quickly, the coach was essentially destroyed above the beltline. That hole
through the firewall turned what might have been an underhood fire into a
total loss -- 'tho' he did buy it back and sell off all of the un-touched
running gear.

I won't have any added holes in my firewall!

Ken H.

> So beyond the compressor change it sounds like I need to do some duct
> modifications to make my system cool better. I’ve read that the
> modification
> moderately improve the cooling. I did see someone’s posting about adding
> his own separate routing of air con venting that had vents on the
> floorboard of the driver and passenger side. Just was wondering on that
> kind of mode worth it? If not, all good, I can just make the ductile modes
> and put it back together. If I dig into this I’m just trying to get the
> best end result.
>
> Thanks,
> TG
> --
> Tom Geiger
> 76 Eleganza II
> KCMO
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
 
The ducting changed over the years. With a 76 you should have that “add-on” lower max air duct GM used until the 77 redesign. If that is working
you shouldn’t need to do more duct changes.
--
John Lebetski
Woodstock, IL
77 Eleganza II
 
It is not that any GMC AC system is bad. For the era in which they were
designed and used, (40+ years ago) they were state of the art.
But modern cars have many improvements that the GMC didn’t have. The
biggie? Space!
Inside the GMC is a huge, essentially non insulated, glass enclosed
cavern. Compare that to a modern car, well insulated, 1/4 the size,
darkened glass, and computer controlled systems.
Like comparing eggs to oranges. More differences than similarities.
Can the GMC be improved? Sure can. First, reduce the space that needs
cooled.
Leave that A6 compressor alone. It will cool a 3 bedroom house. Make
sure that all your vacuum motors that open and close work. Most do not.
Insure that all the felt seals/wipers on the edges of the vacuum doors are
intact. Most aren't. Be sure all the cables and controls work properly.
Make darn sure that your hot water to the heater core shuts off completely.
Those in-line vacuum controlled valves usually allow quite a bit of hot
coolant to circulate even when turned off. Many owner report that just
installing a manually operated bypass loop in those two lines made a huge
difference in AC function.
Ok, so you do all that, and you wife's hot flashes still override the
capabilities of the AC system. GOOD LUCK WITH THAT ONE!!.
Jim Hupy
Salem, Oregon

On Sat, Jun 19, 2021, 6:42 AM John R. Lebetski
wrote:

> The ducting changed over the years. With a 76 you should have that
> “add-on” lower max air duct GM used until the 77 redesign. If that is
> working
> you shouldn’t need to do more duct changes.
> --
> John Lebetski
> Woodstock, IL
> 77 Eleganza II
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
 
> Every time I hear someone mention added ductwork I remember John & Linda
> Richardson's battery fire a few years ago: The batteries somehow caught
> fire, causing a raging inferno under the right front hood. Someone had
> added a duct which entered the cockpit just above Linda's feet. The flames
> immediately burned through the duct, passed behind the dash and over her
> head, then followed the roof toward the rear. They got out unharmed,
> somehow, but despite a firetruck being nearby and putting the fire out
> quickly, the coach was essentially destroyed above the beltline. That hole
> through the firewall turned what might have been an underhood fire into a
> total loss -- 'tho' he did buy it back and sell off all of the un-touched
> running gear.
>
> I won't have any added holes in my firewall!
>
> Ken H.

I almost did this mod back in the early 2000s to increase fresh air. I am glad I never got around to it and have avoided adding holes to my GMC's
"firewall".

I am afraid of coach fires. I have 4 automatic fire extinguishers and 5 manual extinguishers on board.

https://www.gmcmotorhome.com/tech/vents/index.html

--
Richard
76 Palm Beach
SE Michigan
www.PalmBeachGMC.com


Roller Cam 455, TBI+EBL, 3.42 FD, 4 Bag, Macerator, Lenzi (brakes, vacuum system, front end stuff), Manny Tranny, vacuum step, Tankless + OEM water
heaters.
 
For sure would not want that to happen guys. That KC’s for the heads up. I’ll pull the box and make the mods and sealing improvements. Check for
all the damper door operations and see if there any issues. Are there any write ups on that part of the restore? There was a plastic manifold that
potentially would have leaks or cracks? Where would I get the metal replacement one? Jim, I will take your recommendation and leave the A6 in place
and run thru all the other items and see how it improves. If good then I’m set, if not then the compressor gets pulled.

Thanks all,
TG
--
Tom Geiger
76 Eleganza II
KCMO
 
Any suggestions about what to do with spare A6's? I know where 5 are in
the storage building -- there may be more hiding somewhere around here.
I've no idea of their conditions -- don't even know which one I removed,
operating, to install the "Sanden".

I will add this to the arguments FOR "Sanden" -- removing most of the cast
iron A6 mounting bracket sure cleans up the engine -- it's even possible to
remove the right rocker cover! :-)

Ken H.

> For sure would not want that to happen guys. That KC’s for the heads up.
> I’ll pull the box and make the mods and sealing improvements. Check for
> all the damper door operations and see if there any issues. Are there any
> write ups on that part of the restore? There was a plastic manifold that
> potentially would have leaks or cracks? Where would I get the metal
> replacement one? Jim, I will take your recommendation and leave the A6 in
> place
> and run thru all the other items and see how it improves. If good then
> I’m set, if not then the compressor gets pulled.
>
> Thanks all,
> TG
> --
> Tom Geiger
> 76 Eleganza II
> KCMO
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
 
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