Vacuum pump for A\C work - PeachParts Mercedes-Benz Forum

dude99 · #1 07-04-2015, 07:42 PM

I'm assembling some tools to do some A\C work and am wondering if the pump I have is good enough.

Its a GAST Vacuum Pump DOA-V720-AA

I got it for free so its no big deal if its no good. I just wanted to know before I got fittings for it if it would do the job or not.

Phil · #2 07-04-2015, 08:55 PM

Do you have your licence? Even if you are working only with 134 it is still a good idea. Are you only working on your own car or are you getting into this to work on others. If you are going to work only on your car that pump might do the job but if you are going to do much of it you might want to get something that works a little faster. Look at how much air volume the pump moves to get an idea how fast it will pull a vacuum. If you want your licence/ certification for automotive HVAC go to this site http://www.epatest.com/ and then go to the 609 section.

tjts1 · #3 07-04-2015, 09:07 PM

Yes the pump is good enough.

Quote:

Originally Posted by Phil

Do you have your licence? Even if you are working only with 134 it is still a good idea. Are you only working on your own car or are you getting into this to work on others. If you are going to work only on your car that pump might do the job but if you are going to do much of it you might want to get something that works a little faster. Look at how much air volume the pump moves to get an idea how fast it will pull a vacuum. If you want your licence/ certification for automotive HVAC go to this site EPA Certification by Mainstream Engineering and then go to the 609 section.

I'm not sure the EPA test is going to do him much good in Vancouver, British Columbia.

Phil · #4 07-04-2015, 10:16 PM

Quote:

Originally Posted by tjts1

Yes the pump is good enough.

I'm not sure the EPA test is going to do him much good in Vancouver, British Columbia.

Oh picky, picky, picky. Opps! I didn't notice that. For any one else then.

dude99 · #5 07-05-2015, 12:23 AM

Thanks, it will only be for my car, so time is not a huge deal.

vstech · #6 07-05-2015, 11:25 AM

I was looking over the site, and that pump is more for scientific work...
Ac work needs deep moisture removing vacuum... I'm trying to find the micron rating for the pump... But, in Canada, the only refrigerant you can buy for cars is the enviro safe propane stuff...and vacuum isn't a necessity with it... So... Sure, use that pump.

vstech · #7 07-05-2015, 11:28 AM

It would work GREAT for testing door locks, and such though...

Charlie Foxtrot · #8 07-05-2015, 02:01 PM

Sorry, but the GAST pump only pulls about 25.5, ac work needs 29.9"hg or better. The purpose of pulling a vacuum is to change the boiling point of water to 70F so that the moisture in the system boils off while you are pulling the vacuum. Of course this assumes that your working environment ambient temp is above 70F. of course you can help the process by warming the various ac components with a heat gun or hair dryer. Good luck!

dude99 · #9 07-06-2015, 12:11 AM

Quote:

enviro safe propane stuff...and vacuum isn't a necessity with it... So... Sure, use that pump.

Really? Could you elaborate on this a little?

Quote:

Sorry, but the GAST pump only pulls about 25.5, ac work needs 29.9"hg or better.

I sort of figured it wasn't enough, oh well.... Temp shouldn't be an issue it was 35*C here today (95*F for you non metric types)...

vstech · #10 07-06-2015, 11:34 AM

Quote:

Originally Posted by dude99

Really? Could you elaborate on this a little?

I sort of figured it wasn't enough, oh well.... Temp shouldn't be an issue it was 35*C here today (95*F for you non metric types)...

In Canada, 12 and 134 are illegal... So the only option is enviro safe... Instructions for enviro safe state, blow out the lines with nitrogen, then blow out with a bit of enviro safe, then charge with about 10% the volume of refrigerant as you would with 12... And adjust charge to maximum cooling...

Keep in mind, the blown out enviro safe is flammable, and you need to be careful of sparks...

dude99 · #11 07-06-2015, 11:38 AM

Interesting....

dude99 · #12 07-06-2015, 11:47 AM

So would pulling a vacuum on the system be completely pointless then or would it still be best practice?

vstech · #13 07-06-2015, 12:01 PM

With that pump, it wouldn't accomplish much.

dude99 · #14 07-06-2015, 12:17 PM

I meant if I were to buy a proper A\C pump

vstech · #15 07-06-2015, 03:20 PM

I'm of the mind that proper vacuum is important no matter what refrigerant you use, because the oil getting moisture in it, becomes acidic...

but the folks at envirosafe don't feel it's necessary.