purge ac system - The 1947 - Present Chevrolet & GMC Truck Message Board Network

domeier · 10-24-2011, 03:35 PM

I have my Old Air ac ready to go, (now that winter's coming, of course,) but I need to purge it before charging with 134, and none of the auto parts shops around here rent vacuum pumps. Any creative suggestions?

buddylee · 10-24-2011, 04:27 PM

there is no shortcut to purging the air. if you dont evacuate all the air , you will only create more problems.
check at a local AC supply house and ask who does side work. one of the guys should be able to come by for 1/2 hour for a couple of beers.
I am an AC- refrigeration guy by trade too far away to help

Ackattack · 10-24-2011, 04:50 PM

I think harbor freight sells them.

You might see if Old air has pumps that you send back to them, ya never know.

PanelDeland · 10-24-2011, 08:07 PM

Just take it to a shop and have them pull a vacuum and charge the system.

domeier · 10-24-2011, 09:46 PM

I picked up an orificed vacuum generator today. It'll take a while to pull it down, but I'm in no hurry.

mrein3 · 10-25-2011, 07:54 AM

I bought an electric pump from Harbor Fright for under $100.
Make sure you get the vacuum down to -28" Hg. Then close off the vacuum and make sure it stays there for 30 minutes.

Getting it down to -28" Hg boils all the water out of the system. Water from the air will kill your AC.

Keeping a vacuum for 30 minutes proves that you have no leaks in the system.

No water and no leaks = happy AC system.

domeier · 10-25-2011, 11:21 AM

I bought the $19.95 vacuum generator from Harbor. We used these on automated cycle purge systems when I worked for a specialty gas systems company. The ones we built would pull 29" on 60 psi of air... but we'll have to see what the HB unit does - if it does anything! I figure for twenty bucks I'll give it a shot. If it doesn't pull, I'll take it back and buy the pump.

I'd like to cycle purge the system, but don't have a supply of dry nitrogen. Best way to remove moisture is about 60 cycles of pressurized N2/hard vacuum back and forth. Pulling straight vacuum leaves moisture in the dead legs of the system. I'm surprised the ac shops don't cycle purge.

mrein3 · 10-25-2011, 12:32 PM

Quote:

Originally Posted by domeier

I'd like to cycle purge the system, but don't have a supply of dry nitrogen. Best way to remove moisture is about 60 cycles of pressurized N2/hard vacuum back and forth. Pulling straight vacuum leaves moisture in the dead legs of the system. I'm surprised the ac shops don't cycle purge.

Probably cost. Between boiling out the water with the vacuum, and the dessicant in the receiver/dryer, it is good enough.

chevytruckluver · 10-25-2011, 02:02 PM

Quote:

Originally Posted by PanelDeland

Just take it to a shop and have them pull a vacuum and charge the system.

Agreed...
If you dont own a pump or cant rent one and charge the system yourself, you should just take it to a shop and have it done.
If you have to buy the pump, will you ever need it again?

domeier · 10-25-2011, 03:51 PM

The $20 vg worked pretty good, but my compressor isn't up to feeding it, so I brought it back to Harbor Freight and bought a pump for $80. I don't go to shops to get any work done on my truck. I don't trust the quality of the wrenchers. Besides, this is fun. I'll use the pump and manifold to recharge my old man's S10, then craigslist it.

48richard · 10-29-2011, 08:02 PM

I borrowed one from Autozone, although I had to put down the whole cost of the thing as a deposit.

domeier · 10-30-2011, 01:10 AM

I wound up buying a pump from harbor freight and got it all finished up a couple days ago. I'll have to get some pics up. Blows nice and cold.

bollybib · 10-30-2011, 12:20 PM

Quote:

Originally Posted by domeier

The $20 vg worked pretty good, but my compressor isn't up to feeding it, so I brought it back to Harbor Freight and bought a pump for $80. I don't go to shops to get any work done on my truck. I don't trust the quality of the wrenchers. Besides, this is fun. I'll use the pump and manifold to recharge my old man's S10, then craigslist it.

An excellent reason IMO.

**leddzepp** · 10-30-2011, 12:23 PM

Quote:

Originally Posted by domeier

I wound up buying a pump from harbor freight and got it all finished up a couple days ago. I'll have to get some pics up. Blows nice and cold.

I have the 2-stage pump from HF, it works like a charm. I have used it on both R-12 and R-134 systems.

domeier · 10-30-2011, 10:45 PM

I can hardly wait for summer. Just have to touch up the firewall paint, and it's all done.

Thanks to everyone who shared tips, and especially Chris, who offered to loan me his vacuum pump, (too late - but it's the thought that counts!) Great bunch of people on this forum.

10-24-2011, 03:35 PM	#1
domeier Registered User Join Date: Sep 2011 Location: San Jose, California Posts: 784	purge ac system I have my Old Air ac ready to go, (now that winter's coming, of course,) but I need to purge it before charging with 134, and none of the auto parts shops around here rent vacuum pumps. Any creative suggestions?

10-24-2011, 04:27 PM	#2
buddylee Registered User Join Date: Jan 2010 Location: Coventry,RI Posts: 114	Re: purge ac system there is no shortcut to purging the air. if you dont evacuate all the air , you will only create more problems. check at a local AC supply house and ask who does side work. one of the guys should be able to come by for 1/2 hour for a couple of beers. I am an AC- refrigeration guy by trade too far away to help

10-24-2011, 04:50 PM	#3
Ackattack Senior Member Join Date: Aug 2002 Location: Valley Center KS Posts: 3,525	Re: purge ac system I think harbor freight sells them. You might see if Old air has pumps that you send back to them, ya never know. __________________ Project Bruiser: 68 Pro-Touring C-10 5.3L / 4L60E Project Ironhide: 97 GMC Crew Cab 4x4 Cummins SOLD: '69 GMC 1/2T SWB TBI'd: Project No Buck Assembly Manual Index Sign up Thread!!! Factory Service Manual Index

10-24-2011, 08:07 PM	#4
PanelDeland I am a Referee of life. Join Date: Jun 2000 Location: Greensboro N.C. Posts: 13,993	Re: purge ac system Just take it to a shop and have them pull a vacuum and charge the system. __________________ The 47-present Chevrolet and GMC Truck Message Board Network,it's owners,moderators,members,and associates of any type should not be held responsible for my opinion. You can't fix stupid,not even with duct tape. "My appearance is due to the fact that "GOD" does punish you for having too much fun!" Barrett-Jackson has perfected alchemy,they make rust into gold! "You can lead a horse to water but you can't saddle a duck" "Cleverly disguised as a 'Responsible Adult' "Sometimes your Knight in shining armor is just a retard in tinfoil"

10-24-2011, 09:46 PM	#5
domeier Registered User Join Date: Sep 2011 Location: San Jose, California Posts: 784	Re: purge ac system I picked up an orificed vacuum generator today. It'll take a while to pull it down, but I'm in no hurry.

10-25-2011, 07:54 AM	#6
mrein3 Registered User Join Date: Feb 2000 Location: Center City, MN, USA Posts: 3,253	Re: purge ac system I bought an electric pump from Harbor Fright for under $100. Make sure you get the vacuum down to -28" Hg. Then close off the vacuum and make sure it stays there for 30 minutes. Getting it down to -28" Hg boils all the water out of the system. Water from the air will kill your AC. Keeping a vacuum for 30 minutes proves that you have no leaks in the system. No water and no leaks = happy AC system. __________________ '70 cab, '71 chassis, 383, TH350, NP205. '71 Malibu convertible '72 Malibu hard top Center City, MN

10-25-2011, 11:21 AM	#7
domeier Registered User Join Date: Sep 2011 Location: San Jose, California Posts: 784	Re: purge ac system I bought the $19.95 vacuum generator from Harbor. We used these on automated cycle purge systems when I worked for a specialty gas systems company. The ones we built would pull 29" on 60 psi of air... but we'll have to see what the HB unit does - if it does anything! I figure for twenty bucks I'll give it a shot. If it doesn't pull, I'll take it back and buy the pump. I'd like to cycle purge the system, but don't have a supply of dry nitrogen. Best way to remove moisture is about 60 cycles of pressurized N2/hard vacuum back and forth. Pulling straight vacuum leaves moisture in the dead legs of the system. I'm surprised the ac shops don't cycle purge.

10-25-2011, 03:51 PM	#10
domeier Registered User Join Date: Sep 2011 Location: San Jose, California Posts: 784	Re: purge ac system The $20 vg worked pretty good, but my compressor isn't up to feeding it, so I brought it back to Harbor Freight and bought a pump for $80. I don't go to shops to get any work done on my truck. I don't trust the quality of the wrenchers. Besides, this is fun. I'll use the pump and manifold to recharge my old man's S10, then craigslist it.

10-29-2011, 08:02 PM	#11
48richard Registered User Join Date: Oct 2009 Location: Phoenix, AZ Posts: 475	Re: purge ac system I borrowed one from Autozone, although I had to put down the whole cost of the thing as a deposit. __________________ 1971 C10 Longbed, 350/TH350

10-30-2011, 01:10 AM	#12
domeier Registered User Join Date: Sep 2011 Location: San Jose, California Posts: 784	Re: purge ac system I wound up buying a pump from harbor freight and got it all finished up a couple days ago. I'll have to get some pics up. Blows nice and cold.

10-30-2011, 10:45 PM	#15
domeier Registered User Join Date: Sep 2011 Location: San Jose, California Posts: 784	Re: purge ac system I can hardly wait for summer. Just have to touch up the firewall paint, and it's all done. Thanks to everyone who shared tips, and especially Chris, who offered to loan me his vacuum pump, (too late - but it's the thought that counts!) Great bunch of people on this forum. Attached Images



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