Larry,
I just returned in my GMC from Arkansas where before the rain started this
weekend the temps were near 100 at Little Rock. As I drove I-40 I had plenty of
time to twiddle with the air conditioner controls to try to coax the most
cooling out of the dash vents I could get. So, your post is most timely in my
case.
I don't know whether the modifications recommended to you by the former GMC
owner would help, but it seems that you might first need know which of the air
flow variations you are working with. In Zay Brand's article on the GMC AC
system ( see B. Masseys site at
http://www.web-access.net/~bmassey/air_conditing.html ), there are air four
systems described: 1) early '73, 2) later '73 and '74 with 'max air' and 80%
blower inlet air from inside, 3) '75 and '76 "Type 2" with 100% external or
reirc air return flow, and 4) '77 and '78 with major dash and vent redesign with
return to 80% interior inlet air return.. Which system do you have that the
former owner suggested the changes for?
Thanks,
Phil Stewart
'76 Transmode TN
> Hey, gang, I am here in sunny Oklahoma City for an AAU girls b-ball
> tournament. Stayed at the East OKC KOA last night. As I was cleaning the
> windshield this morning, I heard, from behind....."best damned motorhome ever
> built!"....
>
> This old gentleman had quite a history with GMC's. (Of course he was driving
> a SOB). He told me about a modification to the A/C dash air that I wanted to
> bounce of the NET. It goes like this. He pointed to the plastic ducting that
> is over the battery, and said that was the return. He said to cut a round
> hole in that and add a collar to install some flex duct to it. Then he
> pointed to the opening in the top and front of the blower box. He said to
> make a sheetmetal cover for that. It should fit over the "hole" on the front
> and up over the top to within a short distance of the back of the "hole"
> where the diaphragm is. It will not completely block off the "hole"....then
> attach an oblong collar to that sheetmetal, and fit the other end of the duct
> to it. He said you will not believe the difference in the dash air. He also
> recommended fitting a tight fitting door to the exterior of the range hood,
> as it is a major source of a/c leakage.
> Just wanted to see if anyone has heard of the a/c dash air mod, and solicit
> comments. Heading to Golden, CO next, after a quick trip back home to
> Springfield for a few days. Larry Nelson in MO, PB75
I just returned in my GMC from Arkansas where before the rain started this
weekend the temps were near 100 at Little Rock. As I drove I-40 I had plenty of
time to twiddle with the air conditioner controls to try to coax the most
cooling out of the dash vents I could get. So, your post is most timely in my
case.
I don't know whether the modifications recommended to you by the former GMC
owner would help, but it seems that you might first need know which of the air
flow variations you are working with. In Zay Brand's article on the GMC AC
system ( see B. Masseys site at
http://www.web-access.net/~bmassey/air_conditing.html ), there are air four
systems described: 1) early '73, 2) later '73 and '74 with 'max air' and 80%
blower inlet air from inside, 3) '75 and '76 "Type 2" with 100% external or
reirc air return flow, and 4) '77 and '78 with major dash and vent redesign with
return to 80% interior inlet air return.. Which system do you have that the
former owner suggested the changes for?
Thanks,
Phil Stewart
'76 Transmode TN
> Hey, gang, I am here in sunny Oklahoma City for an AAU girls b-ball
> tournament. Stayed at the East OKC KOA last night. As I was cleaning the
> windshield this morning, I heard, from behind....."best damned motorhome ever
> built!"....
>
> This old gentleman had quite a history with GMC's. (Of course he was driving
> a SOB). He told me about a modification to the A/C dash air that I wanted to
> bounce of the NET. It goes like this. He pointed to the plastic ducting that
> is over the battery, and said that was the return. He said to cut a round
> hole in that and add a collar to install some flex duct to it. Then he
> pointed to the opening in the top and front of the blower box. He said to
> make a sheetmetal cover for that. It should fit over the "hole" on the front
> and up over the top to within a short distance of the back of the "hole"
> where the diaphragm is. It will not completely block off the "hole"....then
> attach an oblong collar to that sheetmetal, and fit the other end of the duct
> to it. He said you will not believe the difference in the dash air. He also
> recommended fitting a tight fitting door to the exterior of the range hood,
> as it is a major source of a/c leakage.
> Just wanted to see if anyone has heard of the a/c dash air mod, and solicit
> comments. Heading to Golden, CO next, after a quick trip back home to
> Springfield for a few days. Larry Nelson in MO, PB75
