Vacuum Pump for Car A/C

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  #1  
Old 07-02-11, 09:10 AM
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Vacuum Pump for Car A/C

Does anyone ever use this Harbor Freight's vacuum pump (Air Vacuum Pump with R134A and R12 Connectors) on their car A/C to suck out air in A/C system? Does it work well?
 
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Old 07-02-11, 10:24 AM
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Dealt with venturi bilge pumps in the Navy. They never worked worth a crap. Can't imagine a venturi vacuum pump.
 
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Old 07-02-11, 09:00 PM
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I suppose the $64,000 question is whether you have a compressor that will provide 4.2 CFM @ 90 PSI. The reviews seem pretty good, although one mentions adapter hose and another the volume of air required to operate it. It's certainly not meant for anything approaching daily or professional use I wouldn't think, but for the price if it worked good a few times it probably paid for itself.
 
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Old 07-03-11, 06:36 AM
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where did the $64,000 come from?
 
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Old 07-03-11, 07:06 AM
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$64,000 Question

It is a shame that Harbor Freight would falsely claim that their venturi vacuum device would remove moisture from an a/c system!

In the refrigeration trade the vacuum range that you try to shoot for is actually in microns and not inches.
Microns are a much finer graduation and can easily be measured with a micron guage.

How a vacuum pump removes moisture is by lowering the system pressure to the point that water will begin to boil at lower than room temperature.
For example, in inches to get water to boil at say 50 degF you would have to achieve and maintain 29.66 " of mercury and maintain that for an undetermined amount of time.
The reason the time is undetermined is because you have no way of knowing how much moisture is in the system and how long it would take to boil it out.
29.66" of mercury is also just an example, typical commercial electric vacuum pumps will achieve 29.86 inches and lower which has a corresponding boiling point of 10 degF .

So, 28.3 inches the HF unit can do is indeed a vacuum but I am unsure how it can remove moisture when its corresponding boiling point is around 90 degF.

The bottom line that these boring facts point out is that no, the HF vacuum pump will not remove moisture.
If left on a system long enough with a larger air compressor blowing into it you may remove air but who knows.


This is what you need:

Click image:

Image courtesy of harborfreight.com
 
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Old 07-03-11, 07:16 AM
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Originally Posted by ukrbyk View Post
where did the $64,000 come from?
It came from inflation. When I was a wee lad the popular radio game show $64 question had spawned the cliche phrase "thats the $64 question". In the fifties with the coming of TV that often used phrase beget the TV game show "The 64 million Dollar Question" and the phrase morphed to "thats the 64 million dollar question". Guess someone dropped some zeros.
 
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Old 07-03-11, 07:20 AM
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IIRC it was called the "$64,000 question".
Mike
 
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Old 07-03-11, 07:36 PM
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Tow you are confusing the kids.
 
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Old 07-03-11, 08:07 PM
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IIRC it was called the "$64,000 question".
Mike
You are right I am wrong. I'll shut up now.
 
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Old 07-03-11, 08:22 PM
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I have seen plans for building a vacuum pump using a still working compressor salvaged from a junked refrigerator or freezer. Will those draw down enough? Might be a cheaper alternative for an occasional user if they do.
 
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Old 07-04-11, 03:38 AM
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I have seen attempts at making a vacuum pump from a piston refrigerator compressor but those are not much better than the air venturi type.
They will only remove air and not moisture.

At one time Frigidaire made a rotary fridge compressor that could draw a decent vacuum but those are pretty scarce now.
 
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