Air Con air box modifications

T

tom geiger

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Dec 31, 2006
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Geez, June is almost over. Does anyone have a trick to slow down the summer?
I’m pulling over the motorhome to start updating the air box for improving the dash air conditioning. Seems to be multiple documents and options on
the mod. I’ve attached one I found. Is this the best doc and mod to follow for best results? Going to study the process and then get it done.

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

Appreciate the help,
TG
--
Tom Geiger
76 Eleganza II
KCMO
 
Tom,

That, Zay Brand's paper is what I always recommend.
Ken H.

> Geez, June is almost over. Does anyone have a trick to slow down the
> summer?
> I’m pulling over the motorhome to start updating the air box for improving
> the dash air conditioning. Seems to be multiple documents and options on
> the mod. I’ve attached one I found. Is this the best doc and mod to
> follow for best results? Going to study the process and then get it done.
>
> http://www.gmcws.org/Tech/air_conditioning/air_conditing.html
>
> Appreciate the help,
> TG
> --
> Tom Geiger
> 76 Eleganza II
> KCMO
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
 
That return air modification will make a big difference on your 76.
--
Roy Keen
Minden,NV
76 X Glenbrook
 
Luckily ai have a 77. I’m not sold on hard changes that remove outside air choice
1) you lose ventilation
2) you lose the positive cabin pressure to thwart fumes and sewer odors
3) can’t just have fresh air through vents on cool days
4) you lose the “ram air” effect which realy helps air volume at highway speeds even with fan on 2.
5) you have ‘type 2’ with max air lower duct already
6) no outside air is bad during heating and def use causing steam up of all inside windows and wetting of wall coverings.
7) if it’s 90 out and 125F inside after being parked in sun, outside air over the evaporator will come out cooler than recirced.
Granted if very high humidity there is less latent heat in recirced air, but have not noticed a difference going to recirc.
Consider before deciding.
--
John Lebetski
Woodstock, IL
77 Eleganza II
 
> Luckily ai have a 77. I’m not sold on hard changes that remove outside air choice
> 1) you lose ventilation
> 2) you lose the positive cabin pressure to thwart fumes and sewer odors
> 3) can’t just have fresh air through vents on cool days
> 4) you lose the “ram air” effect which really helps air volume at highway speeds even with fan on 2.
> 5) you have ‘type 2’ with max air lower duct already
> 6) no outside air is bad during heating and def use causing steam up of all inside windows and wetting of wall coverings. Where ‘heat’ would
> normally work, you would need DEF running comp and costing fuel.
> 7) if it’s 90 out and 125F inside after being parked in sun, outside air over the evaporator will come out cooler than recirced.
> Granted if very high humidity there is less latent heat in recirced air, but have not noticed a difference going to recirc.
> Consider before deciding.

Maybe add... With full recirc it's still unlikely that you'd cool the cabin enough to make much of a difference in the cooling coil intake air
temperature: The max air feature sends the cool air past the driver and co-driver and back into the abyss. Maybe a curtain would help that. Ideal
would be a couple dampers to choose the amount of recirc. On a rainy day it would be nice to keep that wet air out of the inside of the coach.



--
Bill Van Vlack
'76 Royale; Guemes Island, Washington; Twin bed, full (DS) side bath, Brazilian Redwood counter and settee tops,455, 6KW generator; new owner a/o mid
November 2015.
 
Can’t speak towards the adjustable damper door because have not dig into this yet but it is making sense. I do have a curtain behind the driver and
passenger that had help when the system was cooling.

Thanks,
TG
--
Tom Geiger
76 Eleganza II
KCMO
 
Bill, On a rainy day you WANT outside air to keep windows from steaming up. Having inside air recirc and not running compressor will fog up in short
order. Opposite of your suggestion.
--
John Lebetski
Woodstock, IL
77 Eleganza II
 
Sure glad I live in Nevada we don’t have Georgia humidity. Rain and defrost problems are like hens teeth in cowboy country.
--
Roy Keen
Minden,NV
76 X Glenbrook
 
I have a PO modified system. Without any out side air. The defrosters
aren't really functional. If we drive thru a cold front torrential rain,
our vision is gone. At 75 miles an hour, in heavy traffic this is not fun
and you become a danger to others. In our emergency panic, nothing would
wipe clean, nothing would clear the glass. Except for Windex, sprayed on,
the alcohol and surfactants saved us from running off the road or over
someone.
Russ

On Tue, Jun 29, 2021, 1:22 PM John R. Lebetski
wrote:

> Bill, On a rainy day you WANT outside air to keep windows from steaming
> up. Having inside air recirc and not running compressor will fog up in short
> order. Opposite of your suggestion.
> --
> John Lebetski
> Woodstock, IL
> 77 Eleganza II
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
 
If the osa intake on your 76 is totally blocked just open the block off a bit maybe 10% osa would do the trick? Where I live 100% osa was never a
problem.
--
Roy Keen
Minden,NV
76 X Glenbrook
 
If the defrost mode gets eliminated on the Brand modification would there be a document that shows a adjustable damper? Is that the GM original 77-78
air intake mod?

Thanks,
TG
--
Tom Geiger
76 Eleganza II
KCMO
 
The stock 77-78 design is like all other “normal” GM vehicles of same years. Compressor runs in non freezing temps Max, Norm and Def. Recirc
only on Max. Heat bleeds a small amount of fresh air to Def vents to prevent nuisance fogging during heat.
Only difference is they deleted the Bilevel graphic from the control head compared to pass car.
--
John Lebetski
Woodstock, IL
77 Eleganza II
 
Roy, sorry, missed what you were meaning on the 10% open aspect. I guess I’ll know what I have once I open it up. Let you know what I find.

Thanks,
TG
--
Tom Geiger
76 Eleganza II
KCMO
 
In my last comment I meant 100% return rather then 100% osa because the humidity here is next to non existent . If you feel a need for more air from
outside just open the closed off factory air intake a little but remember the more 100 degree air you bring into the coach the less you will be able
to cool it.
--
Roy Keen
Minden,NV
76 X Glenbrook
 
So I’ve opened up the box, pretty much stock for a 76 so I’m going to make the recirculation mods and the compressor change. Did take a look at
how the stock squirrel cage fan runs pretty weak at full speed. Is there a higher volume fan that can be put on? Something that makes you know its on
thru the vents?

Thanks,
TG
--
Tom Geiger
76 Eleganza II
KCMO
 
All I can say is after I made the modification suggested by Zay Brand with the osa sealed shut ( remember very little humidity in Nevada) I had a lot
more cold air blowing out of the 2 factory add on vents . There never was a lot of air out of the in dash vents but that wasn’t a problem as long as
the add on factory vents were moving so much air. As far as the blower motor unit I used a blower motor fan unit out of my old work pickup that
bolted right in place of the original probably late 80s my original died of old age.
--
Roy Keen
Minden,NV
76 X Glenbrook
 
Been studying the air con recirculation mods. I do have one question on the hole that gets cut thru the box and firewall. I’m thinking there is a
separation of those surfaces that will need some sort of ducting to enclose that recirculation from interior space back out in the box and get cooled
by the condenser. Does that created portal get lined with metal or am I thinking wrong on this?

Thanks,
Tom
--
Tom Geiger
76 Eleganza II
KCMO
 
If you modify the firewall for return air it should be opened as much as possible to flow as much air as possible . I would put a s creen in front of
it to keep large objects from getting sucked into the blower 1/4” screen would be good . If you feel a need for osa also adj the blocked osa opening
accordingly but leave the new return hole fully open you will want too limit any osa on very hot days.
--
Roy Keen
Minden,NV
76 X Glenbrook
 
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