| [GMCnet] A/C Type 2 Vent question [message #251660] |
Fri, 06 June 2014 19:04  |
Neil Fonville
Messages: 68
Registered: May 2014
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I'm having trouble with the proper vents opening at the right times. I have the service manuals and troubleshooting the vacuum system. Can someone tell me: Does the Type 2 vents on my 75 GMC work in conjunction with the normal dash AC vents or does it close off the dash vents? Thanks, Neil
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1975 GMC II
Allen, TX
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| Re: [GMCnet] A/C Type 2 Vent question [message #251661 is a reply to message #251660] |
Fri, 06 June 2014 19:20  |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Neil,
When you select "A/C" on the top lever and "Recirc" on the lower, the
blower should go to high speed and all air should come from the under-dash
duct -- none from the in-dash louvers. And it should be a real blast of
air. The "High Blower Only" feature can be disabled, enabling you to
select blower speed, by unplugging the orange wire at the right side of the
heater control head.
I must confess that it's been several years since I replaced all that
stuff, so some details may have gotten distorted in my memory. :-(
Ken H.
Americus, GA
'76 X-Birchaven w/Cad500/Howell EFI & EBL,
Manny Brakes & 1-Ton, etc., etc.
www.gmcwipersetc.com
On Fri, Jun 6, 2014 at 8:04 PM, Neil Fonville wrote:
> I'm having trouble with the proper vents opening at the right times. I
> have the service manuals and troubleshooting the vacuum system. Can someone
> tell me: Does the Type 2 vents on my 75 GMC work in conjunction with the
> normal dash AC vents or does it close off the dash vents? Thanks, Neil
> _
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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: [GMCnet] A/C Type 2 Vent question [message #251667 is a reply to message #251662] |
Fri, 06 June 2014 21:13 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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Neil,
Yes, that album I sent is my completely new box. That works in conjunction
with the completely new dash/instrument panel I'd just completed when I did
it:
http://www.gmcmhphotos.com/photos/g4899-new-dash-panel.html
There have been a couple of people that I know of who've replaced the
entire system with something like you're considering, but none of those
were as compact as yours -- that looks like a good option. I can't tell
whether it includes heat though.
Fact is, the type 2 A/C, with the recirculation mod (as in Zay Brand's
"Separating Hot from Cold"), and Duracool in place of R-12, does a pretty
good job of cooling. The biggest problem is that all of the ducting is so
warped and leaky that you can't get the cold air where you want it. Even
my "completely new" unit still uses the same compressor, condenser, and
evaporator; I just improved the air flow.
Please keep me posted if you replace the HVAC.
Ken
On Fri, Jun 6, 2014 at 8:32 PM, Neil Fonville wrote:
> This is very helpful. When you say you replaced all that stuff, do you
> mean you installed another type of AC system? I have been thinking about
> removing all the components of the current system. Open up the firewall
> and install something like this.
> http://www.oldairproducts.com/catalog/popup_image.php?emID=55 into the
> existing heater/AC coil box. Install new duct hoses, etc. Use the existing
> compressor, etc. Has anyone does a total replacement with something more
> modern?
>
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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: [GMCnet] A/C Type 2 Vent question [message #251708 is a reply to message #251660] |
Sat, 07 June 2014 21:47 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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Neil Fonville wrote on Fri, 06 June 2014 18:04I'm having trouble with the proper vents opening at the right times. I have the service manuals and troubleshooting the vacuum system. Can someone tell me: Does the Type 2 vents on my 75 GMC work in conjunction with the normal dash AC vents or does it close off the dash vents? Thanks, Neil
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All of the GMC HVAC doors are notorious for sticking--even the very latest ones. You need to make sure you have maximum vacuum to the system by checking vacuum at the reservour. I usually spend a half hour during most trips cycling all of the modes and gradually they start to move.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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