Air Con air box modifications [message #365074] |
Mon, 28 June 2021 07:07 |
tgeiger
Messages: 518 Registered: February 2006 Location: kansas city
Karma: -1
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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
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[GMCnet] Re: Air Con air box modifications [message #365079 is a reply to message #365074] |
Mon, 28 June 2021 08:37 |
Ken Henderson
Messages: 8726 Registered: March 2004 Location: Americus, GA
Karma: 9
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Tom,
That, Zay Brand's paper is what I always recommend.
Ken H.
On Mon, Jun 28, 2021, 8:08 AM tom geiger wrote:
> 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
> _______________________________________________
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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Re: Air Con air box modifications [message #365091 is a reply to message #365074] |
Mon, 28 June 2021 16:53 |
JohnL455
Messages: 4447 Registered: October 2006 Location: Woodstock, IL
Karma: 12
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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.
John Lebetski
Woodstock, IL
77 Eleganza II
[Updated on: Mon, 28 June 2021 16:56] Report message to a moderator
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Re: Air Con air box modifications [message #365097 is a reply to message #365091] |
Tue, 29 June 2021 00:04 |
Bill Van Vlack
Messages: 419 Registered: September 2015 Location: Guemes Island, Washington
Karma: 14
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JohnL455 wrote on Mon, 28 June 2021 16:53Luckily 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.
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Re: Air Con air box modifications [message #365101 is a reply to message #365074] |
Tue, 29 June 2021 09:17 |
tgeiger
Messages: 518 Registered: February 2006 Location: kansas city
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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
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Re: Air Con air box modifications [message #365110 is a reply to message #365074] |
Tue, 29 June 2021 12:22 |
JohnL455
Messages: 4447 Registered: October 2006 Location: Woodstock, IL
Karma: 12
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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
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Re: Air Con air box modifications [message #365111 is a reply to message #365091] |
Tue, 29 June 2021 12:22 |
roy1
Messages: 2126 Registered: July 2004 Location: Minden nevada
Karma: 6
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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
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[GMCnet] Re: Air Con air box modifications [message #365115 is a reply to message #365110] |
Tue, 29 June 2021 12:54 |
Russell Mehlenbacher
Messages: 128 Registered: June 2010
Karma: 1
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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:
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Unsubscribe or Change List Options:
Russ & Linda Mehlenbacher
Rochester Hills, Michigan
'76 Eleganza
'74 Sequoia
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Re: Air Con air box modifications [message #365145 is a reply to message #365074] |
Thu, 01 July 2021 06:31 |
tgeiger
Messages: 518 Registered: February 2006 Location: kansas city
Karma: -1
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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
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Re: Air Con air box modifications [message #365148 is a reply to message #365074] |
Thu, 01 July 2021 08:53 |
JohnL455
Messages: 4447 Registered: October 2006 Location: Woodstock, IL
Karma: 12
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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
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Re: Air Con air box modifications [message #365156 is a reply to message #365074] |
Thu, 01 July 2021 16:37 |
tgeiger
Messages: 518 Registered: February 2006 Location: kansas city
Karma: -1
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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
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Re: Air Con air box modifications [message #365200 is a reply to message #365156] |
Fri, 02 July 2021 13:18 |
roy1
Messages: 2126 Registered: July 2004 Location: Minden nevada
Karma: 6
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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
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Re: Air Con air box modifications [message #365229 is a reply to message #365074] |
Sat, 03 July 2021 15:29 |
tgeiger
Messages: 518 Registered: February 2006 Location: kansas city
Karma: -1
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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
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Re: Air Con air box modifications [message #365241 is a reply to message #365229] |
Sun, 04 July 2021 12:56 |
roy1
Messages: 2126 Registered: July 2004 Location: Minden nevada
Karma: 6
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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
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Re: Air Con air box modifications [message #365369 is a reply to message #365074] |
Mon, 12 July 2021 08:42 |
tgeiger
Messages: 518 Registered: February 2006 Location: kansas city
Karma: -1
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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
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Re: Air Con air box modifications [message #365378 is a reply to message #365369] |
Mon, 12 July 2021 12:53 |
roy1
Messages: 2126 Registered: July 2004 Location: Minden nevada
Karma: 6
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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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