Leaky compressor issue solved. I got a Sanden compressor from Applied. Very nice, and simple to install. I flushed it, and put in Oil for R-12. ( got lots of R-12 ) Replaced all electrical components. Now that all works nicely. Next the vacuum components. Nothing works. Is the major problem generally the vacuum valve in the dash control? Then there's the 5 I think diaphragms. It's a 1978 GMC. Bob Dunahugh
Front dash A/C issues
- Thread starter Bob Dunahugh
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> Leaky compressor issue solved. I got a Sanden compressor from Applied. Very nice, and simple to install. I flushed it, and put in Oil for R-12. (
> got lots of R-12 ) Replaced all electrical components. Now that all works nicely. Next the vacuum components. Nothing works. Is the major problem
> generally the vacuum valve in the dash control? Then there's the 5 I think diaphragms. It's a 1978 GMC. Bob Dunahugh
I wouldn't think ALL the diaphragms are bad. The vacuum valve in the dash control is repairable, if that is your problem.
http://www.gmcmhphotos.com/photos/hvac-dash-and-blower-control/p58077-hvac-control-panel-function-switch.html
Here's the 1976 heater/ac vacuum "schematic"
http://www.gmcmhphotos.com/photos/color-hvac-troubleshooting-charts/p22990-hvac-diagram-color-comp.html
I would check that I got vacuum at the "vacuum tank" (upper right hand corner of the color diagram, physically located on the driver side of the
blower box). And go from there.
> got lots of R-12 ) Replaced all electrical components. Now that all works nicely. Next the vacuum components. Nothing works. Is the major problem
> generally the vacuum valve in the dash control? Then there's the 5 I think diaphragms. It's a 1978 GMC. Bob Dunahugh
I wouldn't think ALL the diaphragms are bad. The vacuum valve in the dash control is repairable, if that is your problem.
http://www.gmcmhphotos.com/photos/hvac-dash-and-blower-control/p58077-hvac-control-panel-function-switch.html
Here's the 1976 heater/ac vacuum "schematic"
http://www.gmcmhphotos.com/photos/color-hvac-troubleshooting-charts/p22990-hvac-diagram-color-comp.html
I would check that I got vacuum at the "vacuum tank" (upper right hand corner of the color diagram, physically located on the driver side of the
blower box). And go from there.
The 78 (9) port control valve is available from Jim K for ~ $40. I got the 2 port valve for the heater shut off to clean up and seal.
> Leaky compressor issue solved. I got a Sanden compressor from Applied. Very nice, and simple to install. I flushed it, and put in Oil for R-12. (
> got lots of R-12 ) Replaced all electrical components. Now that all works nicely. Next the vacuum components. Nothing works. Is the major problem
> generally the vacuum valve in the dash control? Then there's the 5 I think diaphragms. It's a 1978 GMC. Bob Dunahugh
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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--
C. Boyd
76 Crestmont
East Tennessee
> Leaky compressor issue solved. I got a Sanden compressor from Applied. Very nice, and simple to install. I flushed it, and put in Oil for R-12. (
> got lots of R-12 ) Replaced all electrical components. Now that all works nicely. Next the vacuum components. Nothing works. Is the major problem
> generally the vacuum valve in the dash control? Then there's the 5 I think diaphragms. It's a 1978 GMC. Bob Dunahugh
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
--
C. Boyd
76 Crestmont
East Tennessee
> > Leaky compressor issue solved. I got a Sanden compressor from Applied. Very nice, and simple to install. I flushed it, and put in Oil for
> > R-12. ( got lots of R-12 ) Replaced all electrical components. Now that all works nicely. Next the vacuum components. Nothing works. Is the major
> > problem generally the vacuum valve in the dash control? Then there's the 5 I think diaphragms. It's a 1978 GMC. Bob Dunahugh
>
> I wouldn't think ALL the diaphragms are bad. The vacuum valve in the dash control is repairable, if that is your problem.
>
> http://www.gmcmhphotos.com/photos/hvac-dash-and-blower-control/p58077-hvac-control-panel-function-switch.html
>
> Here's the 1976 heater/ac vacuum "schematic"
>
> http://www.gmcmhphotos.com/photos/color-hvac-troubleshooting-charts/p22990-hvac-diagram-color-comp.html
>
> I would check that I got vacuum at the "vacuum tank" (upper right hand corner of the color diagram, physically located on the driver side of the
> blower box). And go from there.
That URL above for dash control is the electrical stuff. Here's the vacuum stuff
http://bdub.net/gmcmotorhome.info/heat.html
> > R-12. ( got lots of R-12 ) Replaced all electrical components. Now that all works nicely. Next the vacuum components. Nothing works. Is the major
> > problem generally the vacuum valve in the dash control? Then there's the 5 I think diaphragms. It's a 1978 GMC. Bob Dunahugh
>
> I wouldn't think ALL the diaphragms are bad. The vacuum valve in the dash control is repairable, if that is your problem.
>
> http://www.gmcmhphotos.com/photos/hvac-dash-and-blower-control/p58077-hvac-control-panel-function-switch.html
>
> Here's the 1976 heater/ac vacuum "schematic"
>
> http://www.gmcmhphotos.com/photos/color-hvac-troubleshooting-charts/p22990-hvac-diagram-color-comp.html
>
> I would check that I got vacuum at the "vacuum tank" (upper right hand corner of the color diagram, physically located on the driver side of the
> blower box). And go from there.
That URL above for dash control is the electrical stuff. Here's the vacuum stuff
http://bdub.net/gmcmotorhome.info/heat.html
Usually--- the loss of vacuum is a failed hose in the underhood area due to the harsh environment. Easy to trace. I bet once you have vacuum it
works. No vacuum it defaults to DEF for safety readins.
--
John Lebetski
Woodstock, IL
77 Eleganza II
works. No vacuum it defaults to DEF for safety readins.
--
John Lebetski
Woodstock, IL
77 Eleganza II
Thanks Gary for the info. But I Think the 78 is different then the 76. ( Note. I think.) And I know that the default is to defrost. But it just has vent only. I need to start pulling covers off. Might be a mouse thing. Let you know. Bob Dunahugh
________________________________
From: Bob Dunahugh
Sent: Tuesday, June 20, 2017 8:22 PM
To: gmclist
Subject: Front dash A/C issues
Leaky compressor issue solved. I got a Sanden compressor from Applied. Very nice, and simple to install. I flushed it, and put in Oil for R-12. ( got lots of R-12 ) Replaced all electrical components. Now that all works nicely. Next the vacuum components. Nothing works. Is the major problem generally the vacuum valve in the dash control? Then there's the 5 I think diaphragms. It's a 1978 GMC. Bob Dunahugh
________________________________
From: Bob Dunahugh
Sent: Tuesday, June 20, 2017 8:22 PM
To: gmclist
Subject: Front dash A/C issues
Leaky compressor issue solved. I got a Sanden compressor from Applied. Very nice, and simple to install. I flushed it, and put in Oil for R-12. ( got lots of R-12 ) Replaced all electrical components. Now that all works nicely. Next the vacuum components. Nothing works. Is the major problem generally the vacuum valve in the dash control? Then there's the 5 I think diaphragms. It's a 1978 GMC. Bob Dunahugh
Bob, the vacuum motors open and close flappers in the ducting. On the edges
of the flaps, there was originally a felt like piece of material that
closed off the ducts. Probably make really good mouse nesting materials. My
guess anyway. They are kind of a bugger to get to, but a hand vacuum pump
can easily test the dash pots to see if the diaphragms will still move and
hold the flappers. Stuff never ends, does it?
Jim Hupy
Salem, Or
78 GMC ROYALE 403
> Thanks Gary for the info. But I Think the 78 is different then the 76. (
> Note. I think.) And I know that the default is to defrost. But it just has
> vent only. I need to start pulling covers off. Might be a mouse thing. Let
> you know. Bob Dunahugh
>
>
> ________________________________
> From: Bob Dunahugh
> Sent: Tuesday, June 20, 2017 8:22 PM
> To: gmclist
> Subject: Front dash A/C issues
>
>
> Leaky compressor issue solved. I got a Sanden compressor from Applied.
> Very nice, and simple to install. I flushed it, and put in Oil for R-12. (
> got lots of R-12 ) Replaced all electrical components. Now that all works
> nicely. Next the vacuum components. Nothing works. Is the major problem
> generally the vacuum valve in the dash control? Then there's the 5 I
> think diaphragms. It's a 1978 GMC. Bob Dunahugh
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
of the flaps, there was originally a felt like piece of material that
closed off the ducts. Probably make really good mouse nesting materials. My
guess anyway. They are kind of a bugger to get to, but a hand vacuum pump
can easily test the dash pots to see if the diaphragms will still move and
hold the flappers. Stuff never ends, does it?
Jim Hupy
Salem, Or
78 GMC ROYALE 403
> Thanks Gary for the info. But I Think the 78 is different then the 76. (
> Note. I think.) And I know that the default is to defrost. But it just has
> vent only. I need to start pulling covers off. Might be a mouse thing. Let
> you know. Bob Dunahugh
>
>
> ________________________________
> From: Bob Dunahugh
> Sent: Tuesday, June 20, 2017 8:22 PM
> To: gmclist
> Subject: Front dash A/C issues
>
>
> Leaky compressor issue solved. I got a Sanden compressor from Applied.
> Very nice, and simple to install. I flushed it, and put in Oil for R-12. (
> got lots of R-12 ) Replaced all electrical components. Now that all works
> nicely. Next the vacuum components. Nothing works. Is the major problem
> generally the vacuum valve in the dash control? Then there's the 5 I
> think diaphragms. It's a 1978 GMC. Bob Dunahugh
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
