| A/C charging question [message #84822] |
Sun, 16 May 2010 10:09  |
Monte Jestes
Messages: 19
Registered: April 2004
Location: Stillwater, Okla
Karma: -1
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Junior Member |
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Suburban A/C was 134a - low side measured 20 psi with compressor running, 50 psi with compressor off. Not very cool dash air.
I added a can of Duracool in and now have 30 psi with compressor on. Cool dash air - but compressor no longer cycles.
I bought an adapter to check high side. I have the same readings on both low and high fittings?
I am now at a loss. All documentation never mentions the low side pressure varying with on and off compressor.
Monte in Okla
76 Birchaven 23
77 Eleganza 26 (under complete restoration)
75 Eleganza 26 almost completely redone
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| Re: [GMCnet] A/C charging question [message #84824 is a reply to message #84822] |
Sun, 16 May 2010 10:39  |
Steven Ferguson
Messages: 3447
Registered: May 2006
Karma: 0
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Senior Member |
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Monte,
Do you have an electric fan for the condenser? The reason I'm asking
is that if that fan is inop, you will always see high pressure on both
sides and very little cooling. If you can't cool the compressor,
you'll never get it to work right.
The AC in my Caprice wagon was starting to flag as it loses about a
can of R134 a year. Two days ago, a mysterious leak bled off all the
134 so I took that opportunity to switch over to Duracool (HC12a) I
added one can and that thing puts out 29 deg at idle, 27 deg air when
moving 85 deg outside temp). I need to add a bit more and bring the
temp up to the upper 30s. This works well in our 10 percent humidity
but will ice the evaporator over in any kind of humidity.
On Sun, May 16, 2010 at 8:09 AM, Monte Jestes <monte@jestes.net> wrote:
>
>
> Suburban A/C was 134a - low side measured 20 psi with compressor running, 50 psi with compressor off. Not very cool dash air.
> I added a can of Duracool in and now have 30 psi with compressor on. Cool dash air - but compressor no longer cycles.
>
> I bought an adapter to check high side. I have the same readings on both low and high fittings?
>
> I am now at a loss. All documentation never mentions the low side pressure varying with on and off compressor.
>
> --
> Monte in Okla
> 76 Birchaven 23
> 77 Eleganza 26 (under complete restoration)
>
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
--
Steve Ferguson
'76 EII
Sierra Vista, AZ
Urethane bushing source
www.bdub.net/ferguson/
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| Re: A/C charging question [message #84827 is a reply to message #84822] |
Sun, 16 May 2010 11:08 |
idrob
Messages: 645
Registered: January 2005
Location: Central Idaho
Karma: 0
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Senior Member |
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| Monte Jestes wrote on Sun, 16 May 2010 08:09 |
Suburban A/C was 134a - low side measured 20 psi with compressor running, 50 psi with compressor off. Not very cool dash air.
I added a can of Duracool in and now have 30 psi with compressor on. Cool dash air - but compressor no longer cycles.
I bought an adapter to check high side. I have the same readings on both low and high fittings?
I am now at a loss. All documentation never mentions the low side pressure varying with on and off compressor.
|
As the compressor cycles the pressure will change on both the high side and the low side. The pressures will be the same on each sided after a few minutes when the system is shut down or the compressor is not running.
I don't have any suggestions for a 134-12A mix for pressure you might look for, but Steve F's comments are probably a good guideline.
If the compressor cycled with only the 134 in it, but was not very cold, probably it was cycling due to the low suction pressure switch functioning (that is not enough refrigerant). By adding a full can of 12A, you may have overcharged it, which with 12A causes problems.
Emory may chime in here, he is the best man for 12 A answers.
Rob Allen
former owner of '76 x-PB
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| Re: A/C charging question [message #84836 is a reply to message #84822] |
Sun, 16 May 2010 12:24 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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Senior Member |
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Monte;
When you check the suction pressure make sure the engine is at around 1500 RPM it should be around 25-30 lbs with your Duracool 134 mix which won't hurt a thing. If the liquid line is getting hot you may need to mist the condenser with water as you are adjusting the charge . As Steve pointed out you may not be moving enough air over the condenser.
Roy
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: A/C charging question [message #84839 is a reply to message #84822] |
Sun, 16 May 2010 13:01 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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Can you mix Duracool and 134a? I did not know that.
What about R12 and HC12 can they mix? As far as 134a and R12 mixing I would say big no no from what I know.
If adding HC12 to a 134a system, why not just go all HC12 as its so cheap?
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: A/C charging question [message #84851 is a reply to message #84822] |
Sun, 16 May 2010 15:15 |
Wayne
Messages: 106
Registered: August 2004
Karma: 0
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Senior Member |
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Don't know what the pressure is supposed to be in your suburban. On mine, 1994, there is a cycling switch that turns on the comp at about 22+/- lb, and off at 40 +/- lbs. I had to replace my switch .
If you also have a rear a/c it takes more dura cool.
I have mixed Dura cool and R12 and with 134. The instructions say to add Dura cool to the same pressure as whatever was in it(r12 or 134). When you check the pressure you must rev the engine to 1500 +.
Wayne Lawrence
76 Birchaven
Bellflower CA
w.lawrence@verizon.net
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| Re: [GMCnet] A/C charging question [message #84857 is a reply to message #84846] |
Sun, 16 May 2010 17:15 |
Steven Ferguson
Messages: 3447
Registered: May 2006
Karma: 0
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Senior Member |
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I agree with you Rob,
But that's not what he asked. In this country, it is illegal to
bleed the R134a into the atmosphere. You have to pay someone to
evacuate the system and of course, being licensed, they cannot and
will not install the HC12a.
On Sun, May 16, 2010 at 12:43 PM, Rob Mueller <robmueller@iinet.net.au> wrote:
> Steve,
>
> I just re-read Emery's presentation from Pueblo on A/C and considering that
> Duracool is $6-8 per can with a system requirement of 2-3 cans it seems to
> me that bleeding whatever is in the system out and refilling it with
> Duracool the best way to go.
>
> Regards,
> Rob Mueller
> Sydney, Australia
> AUS '75 Avion-The Blue Streak TZE365V100428
> USA '75 Avion-Double Trouble TZE365V100426
>
>
> -----Original Message-----
> From: gmclist-bounces@temp.gmcnet.org
> [mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Steven Ferguson
> Sent: Monday, 17 May 2010 5:09 AM
> To: gmclist@temp.gmcnet.org
> Subject: Re: [GMCnet] A/C charging question
>
> Sure!
>
> Steve Ferguson
>
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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--
Steve Ferguson
'76 EII
Sierra Vista, AZ
Urethane bushing source
www.bdub.net/ferguson/
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| Re: [GMCnet] A/C charging question [message #84858 is a reply to message #84857] |
Sun, 16 May 2010 18:06 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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Steve,
Aha! That must be why when you import a second hand vehicle into Australia
the A/C system has to be open to the atmosphere! They don't want people
dumping R134a into the atmosphere above Australia and increasing the hole in
the Ozone layer as the UV here is high enough already!
As Emery noted in his presentation they have been using propane based
refrigerants here for years!
Regards,
Rob Mueller
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426
-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org
[mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Steven Ferguson
Sent: Monday, 17 May 2010 8:16 AM
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] A/C charging question
I agree with you Rob,
But that's not what he asked. In this country, it is illegal to
bleed the R134a into the atmosphere. You have to pay someone to
evacuate the system and of course, being licensed, they cannot and
will not install the HC12a.
--
Steve Ferguson
'76 EII
Sierra Vista, AZ
Urethane bushing source
www.bdub.net/ferguson/
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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