A/C head pressure

[gworobec]

Just changed out the clutch on the A6 and would like some input on high side head pressure. Currently using R-134 but I know lots of folks use Duracool. Questions are: what is an optimum high side head pressure for R134 and does using Duracool allow for a lower high side head pressure.

thanks

Gary Worobec
gtw5
1973 23 GMC Glacier
Howell EFI/EBL

 

[Matt Colie]

> Just changed out the clutch on the A6 and would like some input on high side head pressure. Currently using R-134 but I know lots of folks use
> Duracool. Questions are: what is an optimum high side head pressure for R134 and does using Duracool allow for a lower high side head pressure.
>
> thanks
>
> Gary Worobec

Gary,

The system Head Pressure will be completely dependent on other things. Most notable will be the ambient air temperature. I have not managed to
secure a full set of HC-12a Thermodymanic data, but it is not for a lack of trying. This is improving, but I have a BOOK still for R-12 and that has
not been duplicated for HC-12a Yet.

If you under charge the system, the evaporator pressure will go low and there is a good chance you will freeze up the evaporator.
If you over charge the system (now so much the the compressor hydraulic locks) the biggest issue will be the loss of condenser area as it will be
flooded in the lower sections.

If you do an internet search for HC-12a, there are a few pressure/temperature charts that are available.

Matt

--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit

 

[robert mueller]

Gary,

Here's a link to the presentation Emery Stora made at a GMCMI convention, I GA-RON-TEE you will be sold on Duracool after reading
it. The last few pages provide detailed instructions on how to fill the A/C system.

http://www.gmcmi.com/wp-content/uploads/2017/04/Duracool-updated-Mar-2017.pdf

Here's a link to the Dura Cool home page:

http://www.duracool.com/

Here's a link to the Frosty Cool home page:

http://frostycool.com/

I have run Dura Cool and Frosty Cool in Double Trouble and could not detect any difference in the performance of the dash a/c.

I also have it in my 1995 Jeep Grand Cherokee and it works fine.

Regards,
Rob M.
The Pedantic Mechanic
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
USA '77 Kingsley - TZE 267V100808


-----Original Message-----
From: Gmclist [mailto:gmclist-bounces] On Behalf Of Gary Worobec
Sent: Sunday, October 15, 2017 2:44 AM
To: Gmclist
Subject: [GMCnet] A/C head pressure

Just changed out the clutch on the A6 and would like some input on high side head pressure. Currently using R-134 but I know lots of
folks use Duracool. Questions are: what is an optimum high side head pressure for R134 and does using Duracool allow for a lower
high side head pressure.

thanks

Gary Worobec
gtw5
1973 23 GMC Glacier
Howell EFI/EBL

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[gworobec]

Thanks Rob

>
> Gary,
>
> Here's a link to the presentation Emery Stora made at a GMCMI convention, I GA-RON-TEE you will be sold on Duracool after reading
> it. The last few pages provide detailed instructions on how to fill the A/C system.
>
> http://www.gmcmi.com/wp-content/uploads/2017/04/Duracool-updated-Mar-2017.pdf
>
> Here's a link to the Dura Cool home page:
>
> http://www.duracool.com/
>
> Here's a link to the Frosty Cool home page:
>
> http://frostycool.com/
>
> I have run Dura Cool and Frosty Cool in Double Trouble and could not detect any difference in the performance of the dash a/c.
>
> I also have it in my 1995 Jeep Grand Cherokee and it works fine.
>
> Regards,
> Rob M.
> The Pedantic Mechanic
> Sydney, Australia
> AUS '75 Avion - The Blue Streak TZE365V100428
> USA '75 Avion - Double Trouble TZE365V100426
> USA '77 Kingsley - TZE 267V100808
>
>
> -----Original Message-----
> From: Gmclist [mailto:gmclist-bounces] On Behalf Of Gary Worobec
> Sent: Sunday, October 15, 2017 2:44 AM
> To: Gmclist
> Subject: [GMCnet] A/C head pressure
>
> Just changed out the clutch on the A6 and would like some input on high side head pressure. Currently using R-134 but I know lots of
> folks use Duracool. Questions are: what is an optimum high side head pressure for R134 and does using Duracool allow for a lower
> high side head pressure.
>
> thanks
>
>
> Gary Worobec
> gtw5
> 1973 23 GMC Glacier
> Howell EFI/EBL
>
>
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

Gary Worobec
gtw5
1973 23 GMC Glacier
Howell EFI/EBL

 

[john r. lebetski]

You can find lots of charts for R12 and 134a on line that work off temp/humidity. The rough rule of thumb is that 134a high side will go higher than
R12 (134a can get above 300PSI ) and HC12 will be lower than R12 as a guideline.
--
John Lebetski
Woodstock, IL
77 Eleganza II

 

[Ken B]

I seldom look at high side pressure on R-134 systems. There are too many variables for an accurate diagnosis in my opinion.

I got burned once by not looking at the high side presssure. My Colorado would start cycling more that normal when the outside temp went over 90 to
95. I eventually, after many trial and errors and several months, found that there was too much r-134 in the system and that the high side trigger
point for the computer was 417 PSI. Removing just a Little R-134 took care of the problem. In the last 10 years on that same vehicle I have looked
at the high side a couple of times and on a hot day pressure in the middle 300's appears to be normal.

I do not know if that helped or not.

Ken B.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

 

[roy keen]

The safest and easiest way to charge any system would be to weigh in the charge as per the mfg specs for the vehicle. On a warm day it generally is
necessary to mist the condenser with a garden hose to keep head presser in check while charging the system.
--
Roy Keen
Minden,NV
76 X Glenbrook

 

[Ken B]

While that is the modern way to charge a system, I have worked on several vehicles that have needed to be tweeked after using the weight method. On
my Colorado it was charged three times by weight using two different machines. It still ended up being over charged. I have worked on several new
Hondas that were checked by dealers using the weight method only to have them freeze up from being undercharged. My Blazer was charged using weight
and a machine only to end up slightly under charged. So charge by weight and be prepared to get out the gauges if it needs a little tweeking.

I charge a completely empty r-134 system using a 30 pound bottle and a set of scales. Usually that is close enough.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

 

[roy keen]

I can see that happening if the a/c had a wrong label on it. In my experience I never had a problem with the hundreds of package units I charged in
the trade. However I only charged a few dozen vehicles in which I used a commercial charging cylinder to weigh in the charge, in each case they were a
correct charge but as you and I know a good set of Gage's are also needed to conferm the results. A lot of times the mechanical engine fan doesn't
't move enough air at idle so the condenser needs a cooling mist if it is idled for very long,
--
Roy Keen
Minden,NV
76 X Glenbrook