Will this vaccumn pump work for our 911 AC?

rnln · 09-04-2007, 02:56 PM

I found a vaccumn pump on Harbor Freight site and wonder if it would work for our car AC? If it does, it would anable DIY swaping the 134 refill fitting adapters.
Anyone know if it would work? In 2 mins, really?
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=92475

scottb · 09-04-2007, 02:59 PM

Don't waste your time or money. If you're going to do a/c work, get a "real" vacuum pump. You can find them on eBay.

Hugh R · 09-04-2007, 02:59 PM

I've been repeatedly told those are not what you want. The ones you want cost about $300. The air powered ones don't pull enough of a vacuum. Having said that, I know someone who used it on his SC and he got cold air.

Scott R · Scott R's Garage

Nope. Go with a Robinaire.

dad911 · 09-04-2007, 04:22 PM

I never used it for A/C, but I do know it won't pull enough of a vacuum to bleed brakes. It uses ALOT of air from your compressor (venturi).

rnln · 09-04-2007, 04:51 PM

Got it. Thank you all.

Tim Hancock · 09-04-2007, 05:01 PM

Quote:

Originally Posted by rnln

I found a vaccumn pump on Harbor Freight site and wonder if it would work for our car AC? If it does, it would anable DIY swaping the 134 refill fitting adapters.
Anyone know if it would work? In 2 mins, really?
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=92475

I have heard of many people using them, but they are not going to do a very good job "boiling out" all of the moisture. One can get somewhat cold air simply by charging without pulling a vacuum first, but without a doubt the moist air still in the system will lead to problems long term.

The venturi style pumps IMO, would be better than no vacuum pump, but if you want your AC components to last long term, you really should use a proper electric motor driven vacuum pump. Moisture from air clings to the inside surfaces of the system and to remove almost all of it, a good vacuum needs to be hooked to the system for a decent length of time. Water "boils" at a lower temperature at lower pressures and what you are trying to do with vacuum is not only remove the water vapor containing air, but also remove the moisture clinging to every nook and cranny in the system.

IOW, the venturi pump is better than nothing, but not near good enough for a system that you want to last a long time.

tab tanner · 05:10 AM

Or just take out the compressor from an old fridge or freezer. I have one I made up 10 years ago and I still use it. First get one that works, plug the unit it and make sure it runs, then just hack away and remove the compressor. When you plug it in you will find that there are lines that have vacum and a few that have presure. Pinch of all but one vaccum and one pressure line. I just took an old freon fitting off an old R134-a 30lb can and cleaned it real well and soldered it to the vaccum pipe on the compessor. IT WORKS GREAT!!!!!!!!!!!!!!! And I got it for free!!!

rnln · 07:09 PM

Tim, Tab,
Thanks for the explanation and idea.

Tab,
amazing, talented.

Again, thanks everyone. Funny that everytime I asked questions about my AC, hoping I can discover the problem and DIY it myself but it always turned out that it's something I have to leave to the pro. In fact, my car has been at the shop several times for AC but still... headache.

Scott R · Scott R's Garage

Quote:

Originally Posted by tab tanner

Or just take out the compressor from an old fridge or freezer. I have one I made up 10 years ago and I still use it. First get on that works, plug the unit it and make sure it runs, then just hack away and remove the compressor. When you plug it in you will find that there are lines that have vacum and a few that have presure. Pinch of all but one vacum and one pressure line. I just took an old freon fitting off an old R134-a 30lb can and cleaned it real well and soldered it to the vacum pipe on the compessor. IT WORKS GREAT!!!!!!!!!!!!!!! And I got it for free!!!

Can you get all the way down to 30 on one of those?

squelch · 09-04-2007, 07:54 PM

I am also looking for an inexpensive solution. I came across this interesting pump:
http://www.silentsucker.com/ but am hesitant to buy one. I think I am just going to keep my eye on craigslist for a used vacuum pump.

Anyone out there have a used one they want to sell?

tab tanner · 05:10 AM

Mine will pull all the way down to 30 inches of vaccum, the best part is it make less noise than my Robinair unit. As a plus you could leave it outside and no one will steal it!!!!

rnln · 09-04-2007, 08:56 PM

squelch,
for $40 bucks, it's even cheaper than Harborfreight stuff. For $40 at HF, you can get a gauge and couple hose. If you ever decide to get this unit, or kow someone who experience it, please post. For that small amout of $$, I love to be able to try it myself. Save and experience.
Thanks.

Scott98 · Scott98's Garage

You have about 40 feet of A/C lines on your 911. You need a REAL vacuum pump that is constantly pulling a vacuum to draw out all of the moisture. The HF boxes are crap. Their great if you just want to see if your system will hold a vacuum but that's it. You can get a rebuilt Robinair pump on e-bay fairly cheaply with a warranty. That's where I bought mine.

Good luck,

Scott

Scott R · Scott R's Garage

Quote:

Originally Posted by tab tanner

Mine will pull all the way down to 30 inches of vacum, the best part is it make less noise than my Robinair unit. As a plus you could leave it outside and no one will steal it!!!!

WOW

My Robinare pulls to 30 inches, however at hefty cost, (and noise) this is a fantastic idea. Cheers to you! I may give this a try with the amount of AC work I do.

tab tanner · 05:09 AM

It is very quite, I'll somtimes leave it on over a weekend to vacuum a 911 which take along time and I have had NO problems with it. I get asked all the time What is that?? I tell them it's a flux capasitor and walk away LOL

Jim Sims · 09-05-2007, 05:50 AM

It is impossible to obtain 30 inches of vacuum in Denver; there is not enough atmospheric pressure at that altitude. Vaccum in inches is measured relative to atmospheric pressure. The bourden tube type pressure/vacuum gages on a refrigeration harness are inaccurate and lack resolution at the pressure (vacuum levels) one is trying to reach: less than 40 microns.

The salvaged refrigerator compressor is an old technique; I recall hearing about it 35 years ago. It however, is a "kludge" and suffers from the problems of low capacity and water contamination which will limit the vacuum one can obtain.

To evacuate a 911 A/C system well, one needs a good two-stage mechanical pump filled with fresh/dry vacuum pump oil pulling on the system for around three hours.

Cheers, Jim Sims

tab tanner · 09-05-2007, 07:03 AM

Vaccum is vaccum correct me if I'm wrong? If you can pull a system down over night I think you will get the same results? Like I said it's cost effective to use a salvaged compressor

Tim Hancock · 09-05-2007, 08:16 AM

Tab, you and I know how many cars you have effectively serviced using your pump over the years, but to boil/outgas the most moisture out of a system using vacuum, the harder the vacuum the better. No doubt, less than optimum pumps are commonly used with satisfactory results, but what Jim is saying is technically the "best" way. I bet on the average, compared with many "chain stores" with poorly maintained professional grade AC equipment along with AC techs who are often not top notch, you are probably doing a better job than many of them even though your homemade pump "might" not remove every last bit of moisture.

While I am not an AC guru, I did get some training on industrial vacuum systems from Varian when I had to design a helium mass spec leak tester. The more hoses, dirt and oil in a system, the harder it is to boil out the last remnants of moisture. Not even Jim's high dollar vacuum pumps will remove EVERY last trace of moisture, but they will do a much better job than the venturi pump originally mentioned in this post.