Home » Public Forums » GMCnet » [GMCnet] A/C vacuum pump
| Re: [GMCnet] A/C vacuum pump [message #326226 is a reply to message #326213] |
Tue, 21 November 2017 18:09   |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Kingsley Coach wrote on Tue, 21 November 2017 14:22Tyler
You've just answered a question I was embarrassed to ask !!
I bought one of those several years ago and never tried it..it looked to cheap to effectively do anything. I think the last time I looked, it was
somewhere in the area of where I keep A/C stuff, which is under the trailer wiring stuff I think, which is right under the last box of crap from my long gone and forgotten Airstream....
Thanks
Mike from NS
Mike,
You should be embarrassed to ask only what the rest of us were born knowing. (That is pretty much nothing.) The rest we got to learn from other's wisdom that they were generous enough to pass to us, our own mistakes and other's mistakes when we are real lucky. This could well be one of those last.
Executive summary for Matt's minor rant.
Don't waste your time and effort, buy a decent pump. At what most shops bill, you can recover the cost with the first use.
<rant on>
That "pump" would be junk for getting a real system to working right.
From published specifications: End point vacuum 28.3 at sea level.
While Antigonish is real close to sea level, 28.3 is not real close to 29.92 (760mm) that is the standard sea level barometer. That is more than 1.5" Hg left in the system. If you use a pump this weak, your only hope to survive is to dry or replace the filter dryer every time the system is open. (That is about 40$C shot right there.)
When R-12 was less then 1$us a pound, we often used to bring a system to can pressure with R-12 and the valve things off and use the pump to pull it down. You can't do that in the coach or any other miniature system like that. Your only hope to have a durable recharge is to pull it down hard. Then fill it with refrigerant. This is a case that I have found no different with R-12, 22, 502, 134a or HC-12(a). But back to the case in hand....
The less expensive pump HF offers if ~100$us. Its published end point if 75µHg (absolute pressure). This will do pretty well, it may not be as good as the 22.5µHg that is promised by the pump that is 50$us more, but for a vehicle A/C system, it (IMHO) serve you well.
If you can manage to get the pump out of someone's dead refrigerator. (They can die from either a leak or a pump failure, so be cautious here.) And set it up with the required fittings, that can work pretty well as they usually can pull 29+". From my experience of years ago, 29.6 will usually be successful.
Why does this matter?
Because if there is any moisture left in the refrigerant circuit, it will collect and freeze that the expansion. That will be the TEX (What a GMC has), capillary used in small stationary units or the orifice used in more modern (cheaper) automotive units. If you are not aware of this problem, it can drive you all the way up the wall trying to figure out why the system seems to work well when it is warm, but as soon as it gets really cranking, it crashes.
I am not going to include the process for drying refrigerant filter/dryers tonight. Maybe some other time. It can be done, but it is neither simpler or easy and requires uncommon tools and equipment.
<rant off>
I am still using the vacuum pump I bought when I was doing refrigeration. That and the flaring block will go with my estate. I don't even want to think about the price to replace those in today's money.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: [GMCnet] A/C vacuum pump [message #326227 is a reply to message #326217] |
Tue, 21 November 2017 18:01 |
Kingsley Coach
Messages: 2691
Registered: March 2009
Location: Nova Scotia Canada
Karma: -34
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Senior Member |
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On a different note, can someone tell me how to remove that bloody AVAST
advertisement from tacking on to my messages..
Thanks again
Virus-free.
www.avast.com
On Tue, Nov 21, 2017 at 5:04 PM, Richard Denney wrote:
> Yahbut....
>
> No, I'm not saying it again.
>
> (I have the same HF pump. Nary a disused icemaker in sight.)
>
> Rick "Too many worthwhile ways to waste a day, not enough wastable days"
> Denney
>
>
> On Tue, Nov 21, 2017 at 10:44 AM Ken Henderson
> wrote:
>
>> "waste a day"? Maybe 30 minutes once the compressor's in hand. Besides,
>> doing stuff like that is 50% of the GMC pleasure! :-)
>>
>> Ken H.
>>
>> On Tue, Nov 21, 2017 at 10:02 AM, Keith V wrote:
>>
>>> I have the HF one also. Life is too short to waste a day making
> something
>>> when I can buy it that cheap.
>>>
>>> It works great.
>>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
> --
> Rick Denney
> 73 x-Glacier 230 "Jaws"
> Off-list email to rick at rickdenney dot com
> _______________________________________________
> GMCnet mailing list
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--
Michael Beaton
1977 Kingsley 26-11
1977 Eleganza II 26-3
Antigonish, NS
Life is too short to hold a grudge; slash some tires and call it even !
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| Re: [GMCnet] A/C vacuum pump [message #326230 is a reply to message #326211] |
Tue, 21 November 2017 19:18 |
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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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Tyler,
Air powered vacuum pump = Vacuum level: 28.3 in. of mercury at sea level
See this chart: https://www.quora.com/What-happens-to-boiling-point-of-water-in-vacuum
Electric vacuum pump = One stage pump draws vacuum down to 75 micron
The air powered pump will not drop the pressure low enough to boil water that is in the system.
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@list.gmcnet.org] On Behalf Of Tyler
Sent: Tuesday, November 21, 2017 11:35 AM
To: gmclist@list.gmcnet.org
Subject: Re: [GMCnet] A/C vacuum pump
If you are really on a budget I have used
https://www.harborfreight.com/air-vacuum-pump-with-r134a-and-r12-connectors-96677.html
the 18$ (and maybe a coupon cheaper) version with satisfactory results on several systems. As good? nope. 70% as good for 15% price?
yep. And certainly good enough to know if system is leaking. A big air compressor helps a lot. I used to use it on a 10 gallon
one...let it charge the air tank, discharge the vacuum pump, shut off vacuum, and recharge air. almost like bleeding brakes old
style. 80 gallon air now, let er rip
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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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| Re: [GMCnet] A/C vacuum pump [message #326242 is a reply to message #326240] |
Wed, 22 November 2017 07:14 |
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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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Rick,
Thanks!
Glad you took the time to clarify what I was saying.
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@list.gmcnet.org] On Behalf Of Richard Denney
Sent: Tuesday, November 21, 2017 11:24 PM
To: gmclist@list.gmcnet.org
Subject: Re: [GMCnet] A/C vacuum pump
Let's be sure to keep things straight, as Rob is doing. The electric pump
in the original post will draw down to 75 microns, which is 29.917 inches
of mercury at sea level. I call that a hard vacuum. It won't survive a
shop's duty cycle, perhaps, but it will work for us if we let it run long
enough. I'll bet shops don't pull a harder vacuum, tough a shop-grade pump
might get there faster.
The air-pressure-operated venturi pump that Tyler posted is the one Matt
(and Rob) warned against. It does not pull a hard enough vacuum to dry an
AC system.
Rick "who got confused" Denney
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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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| Re: [GMCnet] A/C vacuum pump [message #326244 is a reply to message #326242] |
Wed, 22 November 2017 07:23 |
k2gkk
Messages: 4452
Registered: November 2009
Karma: -8
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Senior Member |
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I think I'll head for my local Horror Fright store today to buy one of those!
D C "Mac" Macdonald
Amateur Radio K2GKK
Since 30 November '53
USAF and FAA, Retired
Member GMCMI & Classics
Oklahoma City, OK
"The Money Pit"
TZE166V101966
'76 ex-Palm Beach
k2gkk + hotmail dot com
________________________________
From: Gmclist on behalf of Rob Mueller
Sent: Wednesday, November 22, 2017 07:14
To: gmclist@list.gmcnet.org
Subject: Re: [GMCnet] A/C vacuum pump
Rick,
Thanks!
Glad you took the time to clarify what I was saying.
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@list.gmcnet.org] On Behalf Of Richard Denney
Sent: Tuesday, November 21, 2017 11:24 PM
To: gmclist@list.gmcnet.org
Subject: Re: [GMCnet] A/C vacuum pump
Let's be sure to keep things straight, as Rob is doing. The electric pump
in the original post will draw down to 75 microns, which is 29.917 inches
of mercury at sea level. I call that a hard vacuum. It won't survive a
shop's duty cycle, perhaps, but it will work for us if we let it run long
enough. I'll bet shops don't pull a harder vacuum, tough a shop-grade pump
might get there faster.
The air-pressure-operated venturi pump that Tyler posted is the one Matt
(and Rob) warned against. It does not pull a hard enough vacuum to dry an
AC system.
Rick "who got confused" Denney
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| Re: [GMCnet] A/C vacuum pump [message #326245 is a reply to message #326244] |
Wed, 22 November 2017 07:29 |
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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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Mac,
I would suggest you wait until you need the pump as that way IF it does crap out you'll be covered by the warranty.
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@list.gmcnet.org] On Behalf Of D C _Mac_ Macdonald
Sent: Wednesday, November 22, 2017 7:24 AM
To: gmclist@list.gmcnet.org
Subject: Re: [GMCnet] A/C vacuum pump
I think I'll head for my local Horror Fright store today to buy one of those!
D C "Mac" Macdonald
Amateur Radio K2GKK
Since 30 November '53
USAF and FAA, Retired
Member GMCMI & Classics
Oklahoma City, OK
"The Money Pit"
TZE166V101966
'76 ex-Palm Beach
k2gkk + hotmail dot com
________________________________
From: Gmclist on behalf of Rob Mueller
Sent: Wednesday, November 22, 2017 07:14
To: gmclist@list.gmcnet.org
Subject: Re: [GMCnet] A/C vacuum pump
Rick,
Thanks!
Glad you took the time to clarify what I was saying.
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@list.gmcnet.org] On Behalf Of Richard Denney
Sent: Tuesday, November 21, 2017 11:24 PM
To: gmclist@list.gmcnet.org
Subject: Re: [GMCnet] A/C vacuum pump
Let's be sure to keep things straight, as Rob is doing. The electric pump
in the original post will draw down to 75 microns, which is 29.917 inches
of mercury at sea level. I call that a hard vacuum. It won't survive a
shop's duty cycle, perhaps, but it will work for us if we let it run long
enough. I'll bet shops don't pull a harder vacuum, tough a shop-grade pump
might get there faster.
The air-pressure-operated venturi pump that Tyler posted is the one Matt
(and Rob) warned against. It does not pull a hard enough vacuum to dry an
AC system.
Rick "who got confused" Denney
_______________________________________________
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
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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| Re: [GMCnet] A/C vacuum pump [message #326253 is a reply to message #326191] |
Wed, 22 November 2017 10:24 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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I have a pump the HVAC guy l;eft at one of our sites, along with a 30# cannister of R134a. I forget the make, it's the one which exhausts through the handle. Now, if you keep a vaqcuum overnight and keep the dryer nice and warm for the same time, you will dry it enpugh that it works. You could heat it more and boil off the water which might be in it, but >if< it contains plastic parts you night make a mess of it.
Incidentally, if you have a dog, you can make freezedried treats from liver or chicken with an old pressure cooker by replacing the popoff fitting with a Schrader valve or R134a valve as appropriate for your pump. Hold a vacuum for a couiple of days on a cooker full of treats in the freezer. (You'll need to pass a hose through to the outside, seal it well)
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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