There is a WIDE range in price between the venturi style, air-compressor powered A/C vac pumps and the electric powered ones (like $30 compared to $150). Does anyone here have any experience using one of the "economy" venturi pumps with success? I don't mind buying good tools, but it would be nice to be able to save some $$ on one like this which will get very limited use. __ __ Randy & \ \/ /alerie's \__/olvos '90 245 Estate - '93 965 Estate "Shelby" & "Kate"
If you're comfortable lashing something together, this place
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usually has a selection of new surplus rotary compressors designed for window AC units. I paid less than 10 bucks for mine and another $2 for the capacitor it needed. I soldered a refrigeration fitting onto the inlet pipe and connect my manifold to that. Once it's all hooked up, I set it in a bucket with about 3" of water (well below the electrical terminals!) to keep it cool as there's no refrigerant flowing through it, then fire it up and let it run for about a half hour to pull a nice tight vacuum. It works very well, much better than even real vacuum pumps of the diaphragm type. Yeah, it's ghetto, but I've used it to service probably a dozen automotive AC systems and install several residential heat pump/AC units. You also could look on ebay, a couple years ago I picked up a nice (well, hideous when I got it) Welch Duo-Seal 2 stage vacuum pump for a buck. It looked like it had been dredged from the bottom of a lake, but a thorough cleaning, coat of paint, new oil seal and intake gasket, followed by a couple of days of running flushing oil and then a fresh oil change had it pumping down to under 2 microns. A new pump of that ability is pushing up on $2K. Even the most tired worn out abused rotary vane vacuum pump will work better than an air powered venturi. Heck, a modified bicycle tire pump probably would too.
I did consider that, and it is still a possibility, but I have at least three cars to do (or would like to do) and maybe a fourth so thought having one on hand would/might save in the long run. __ __ Randy & \ \/ /alerie's \__/olvos '90 245 Estate - '93 965 Estate "Shelby" & "Kate"
Don;t bother with the venturi ones, unless you have a VERY large compressor and like making alot of noise. They won't pull a good enough vaccum either really for a/c work.
Better vacuum pumps are capable of 40 microns of mercury or less.
Not sure of the specs on the ones sold by Harbor Freight tools (wwww.harborfreight.com), but they are cheap. For a regular vehicle 2.5 CFM is more than adequate.
Good vacuum importance can never be over emphasized. At least 1/2 hour after reaching max vacuum, 1 hour is better.
You won't get 40 microns without spending over $1,000 if buying new. I'd be shocked if anything from Harbor Freight even approached 1,000 microns, but that said, I did the AC in my 740 years ago with a diaphragm type vacuum pump that didn't even come close to that level and it's been working fine ever since. You can never have too good a vacuum, but a lousy one won't necessarily make the job a failure.
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