five7kid

iTrader: (14)

I'm going to try to get my AC back together and working over the 4th, converting to R134a in the process. Based on the advice of a couple of posts in the past few weeks, I picked up a new receiver/drier, R134a-compatible o-rings, flush, compressor oil, etc. Also have R134a gage kit, can tap.

While at Harbor Freight a couple of months ago, I picked up one of those air venturi vacuum pumps for $12. Do they pull enough vacuum, or should I look into renting a real pump? Or, have it evacuated by a shop before I charge it?

ede

i tihnk i'd just let a shop suck it down. i use to have a pump and traded it back to my snap on man for some stuff i'd get more use out of. every once in a while i wish i still had it.

MightyMouse

I cleaned mine out with a vacuum line from the motor spliced into the ac system. I know this is ghetto but it worked. I just left it on for a few days and figured that the low pressure combined with the high underhood temp would boil off the water. I tried R134a and got a noisy compressor so I switched to a blended hydrocarbon coolant and now I have a system that can be tuned.

Rustynutz

I use a $400 pump that pulls 6 cfm. Usually an hour is enough with this. I cannot imagine what a $12 vacuum pump even looks like.....................................................................................

five7kid

iTrader: (14)

It's smaller than a bread box...

Much smaller. About a 4" cube. Air inlet fitting, gage hose fitting, that's about it.

I'll give it a try and see what kind of vacuum it will produce. Go from there.

Of course, if someone has actually used one...

jeffs82z28

Five 7,
I've not used one, but have always wondered if it would work.
IMHO, if your sub bread box size vacuum pump doesn't do the trick, I would rent a vacuum pump as opposed to having it evacuated.
My reasoning is I don't know if the schrader valves would be able to keep the vacuum from the shop back to your house. After all, they are spring loaded and designed to keep pressure in.

Maybe Ede would know the answer.

Keep us posted, Enquiering minds want to know

Rustynutz

Once the hoses are on and a vacuum is drawn the hoses don't come off until you put pressure in it. The half second it takes to remove a hose is just enough time to suck outside air back into the system. If you had a shop do it they would put a holding charge in it, just enough to give it pressure.
Not sure how you plan on checking to see if the vacuum pump will work, the only way I know to check for good vacuum is with a micron gauge. Can't do it accurate with the inches of mercury side of the manifold gauge set.

Merlin

5-7,

I've use similar vacuum devices for other purposes. The most I've ever seen from an industrial vacuum generator is just over 20" Hg (PIAB vacuum unit). They'll get into a moderate vacuum faster than a mechanical vac pump, but then will take longer to achieve a deep vacuum.

The USEPA requirement for evacuating a ayatem for disposal is to draw and maintain a 10" Hg level. That is enough to boil off all refrigerant at normal (70°F) temperatures or above, but may leave some residual moisture. If you can elevate the system temperature or generate and hold the 10"Hg level for several hours, you'll get 99-44/100ths percent of the moisture out of the system. That's based on my guess that it's about 85°F in Colorado today.

If you can manage to trap the vacuum (with a four-way gauge manifold) you shouldn't have any serious issues. Presuming that you're installing a larger oriface tube with the R-134a, the moisture problem should not be an issue.

Ever thought of using a blend instead of R-134? They are a lot better for cooling efficiency - something like 30% better than R-134a.

jeffs82z28

In a perfect world where time doesn't equal money and the fact that the standard guage set has been used for more years than I care to recall, and most importantly, the 28-30 Inches of vacuum (taking into consideration that the guage is inherantly in-accurate, and a perfect vacuum is un-obtainable with out the help of the government) is sufficiant to boil off enough moisture that it will not cause problems in the system.

That is a major reason for replacement of the accumulator whenever the system is opened up.

eightTfourTA

iTrader: (3)

I have one of those little venturi pumps, and it does just fine for me. Not sure about yours, but mine needs to be run on at least 90psi to pull a 28-30Hg vac. I run it on 115-120psi and it works relatively well; but that's with the benefit of the shop air compressor at work, otherwise i'd be SOL.

five7kid

iTrader: (14)

I managed to get it hooked up - had to take it apart because of fitting incompatibility with my R134a gage kit. With my 90 psi air compressor capacity, it pulled about 24 in-Hg. I had it on for about 1/2 hour when I discovered the '87 compressor I was installing had a two-pole high-side switch, while the '86 uses a single pole. The switch wouldn't come out of the frozen-up '86 compressor, so I'm shut down until I can get a new switch.

Oh, it was about 90 degrees here today. Not sure what the humidity was, except that it was low...