Vacuum Pump For Air Conditioner Service

[Squddle]

Howdy!
I was trying to find an inexpensive vacuum pump to service my air conditioner on my car. These seem to be the cheapest, but since I've never used one before, I have no idea if it would work very well... The cheapest electric ones I've seen are $60.00 from china. These average $20 or so. Anyone have any experience with these things or any vacuum pumps? This one connects to an air compressor.

 

[wornoutoldman]

Yep those work fine.

 

[Squddle]

Do I need a big compressor? I only have a small one I got at Walmart with a small tank

 

[wornoutoldman]

Do I need a big compressor? I only have a small one I got at Walmart with a small tank

Just let your compressor run. As long as it's moving air the diagphram in that pump will work and pull a vacuum on your a/c sytem.

 

[GirchyGirchy]

Just let your compressor run. As long as it's moving air the diagphram in that pump will work and pull a vacuum on your a/c sytem.

I'm guessing his compressor isn't made to just sit there and run for long periods of time, like a normal vacuum pump is.

I'd buy this:

http://www.amazon.com/gp/offer-listing/B005CO9GX6/ref=dp_olp_used?ie=UTF8&condition=used

 

[royesses]

Waste of money. It will pull a vacuum, but nowhere near what is required to lower the boiling point of moisture in your system.

The chart below shows how temperature plays a role in the level of vacuum needed to boil water.

Inches of Mercury              Boiling Point of Water °F

26.45                                  120

27.32                                  110

27.99                                  100

28.50                                   90

28.89                                   80

29.18                                   70

29.40                                   60

29.66                                   50

29.71                                   40

29.76                                   30

29.82                                   20

29.86                                   10

All values are at sea level. Subtract 1 inch for each 1000 ft. above sea
level

You'd be lucky to get 15 to 20" hg out of that vacuum pump.

HF has some low cost pumps that are 120 volt and will do the job. Use a 20% off coupon and get one of those for a low cost solution.

It takes time to boil off the moisture so let the pump run for a half hour or more.

 

[bcschief]

Howdy!
I was trying to find an inexpensive vacuum pump to service my air conditioner on my car. These seem to be the cheapest, but since I've never used one before, I have no idea if it would work very well... The cheapest electric ones I've seen are $60.00 from china. These average $20 or so. Anyone have any experience with these things or any vacuum pumps? This one connects to an air compressor.

You can rent a ac vacuum pump from Autozone with there Loan a Tool program the end result is it cost you nothing but you pay for it when you rent it and get all your money back when you return it. If you don't have a permanent need for one.

Brian

 

[theoldwizard1]

You need a >2HP twin cylinder, oil lubed compressor to get even close to evacuating an A/C system with one of those. As mentioned a small one likely will overheat before it gets the job done (if it is even possible).

The HF vacuum pump is not bad, but buy the extended warranty.

Yellow Jacket probably makes the best A/C service tools out there. You get what you pay for.

 

[bonneyman]

Waste of money. It will pull a vacuum, but nowhere near what is required to lower the boiling point of moisture in your system.

The chart below shows how temperature plays a role in the level of vacuum needed to boil water.

Inches of Mercury              Boiling Point of Water °F

26.45                                  120

27.32                                  110

27.99                                  100

28.50                                   90

28.89                                   80

29.18                                   70

29.40                                   60

29.66                                   50

29.71                                   40

29.76                                   30

29.82                                   20

29.86                                   10

All values are at sea level. Subtract 1 inch for each 1000 ft. above sea
level

You'd be lucky to get 15 to 20" hg out of that vacuum pump.

HF has some low cost pumps that are 120 volt and will do the job. Use a 20% off coupon and get one of those for a low cost solution.

It takes time to boil off the moisture so let the pump run for a half hour or more.

Good info. With vacuum pumps, you get what you pay for.

However, most cars now use R-134a, which uses a synthetic oil. And that oil is hygroscopic (absorbs moisture), making it very difficult to remove with vacuum. On newer refrigerants the vacuum pump is merely to get the air and residual freon out of the system. The moisture gets removed by special filter driers.
Not saying he shouldn't use a vacuum pump (he should). But replacing any filter driers in the system to catch the moisture is the best bet.

http://www.tecumseh.com/~/media/Nor...umseh-Guidelines-for-Utilization-of-R134a.pdf

 

[Richard Cranium]

Great info, Thanks for posting the question to the op and thanks for the education to the posters of the answers.
I was at a professional shop with in the last month, Having a tire fixed. And they recharged a persons a/c with the old shake and bake can, And didn't even pull a vac. I asked about a vac. and the kid told me about the same thing about the oil obsorbing the moisture. I will not be getting my a/c serviced there for sure....

 

[Coloshaver]

Waste of money. It will pull a vacuum, but nowhere near what is required to lower the boiling point of moisture in your system.

The chart below shows how temperature plays a role in the level of vacuum needed to boil water.

Inches of Mercury              Boiling Point of Water °F

26.45                                  120

27.32                                  110

27.99                                  100

28.50                                   90

28.89                                   80

29.18                                   70

29.40                                   60

29.66                                   50

29.71                                   40

29.76                                   30

29.82                                   20

29.86                                   10

All values are at sea level. Subtract 1 inch for each 1000 ft. above sea
level

You'd be lucky to get 15 to 20" hg out of that vacuum pump.

HF has some low cost pumps that are 120 volt and will do the job. Use a 20% off coupon and get one of those for a low cost solution.

It takes time to boil off the moisture so let the pump run for a half hour or more.

I bought this one - http://www.harborfreight.com/25-cfm-vacuum-pump-61245.html $80 with a coupon. The best I could get was ~25 in Hg. Oh yeah - I'm at 4,912' ASL.

 

[skruft]

25 inches is a fair amount of vacuum.

 

[Davefr]

I bought this one - http://www.harborfreight.com/25-cfm-vacuum-pump-61245.html $80 with a coupon. The best I could get was ~25 in Hg. Oh yeah - I'm at 4,912' ASL.

You also need some pretty good fittings and hoses to get down below 500 microns.

A lot of the problems people have getting that low is setup related vs pump related.

 

[AA/FC]

25 inches is a fair amount of vacuum.

Sure.... but not for evacuating an A/C system.

 

[jn503084]

Great info, Thanks for posting the question to the op and thanks for the education to the posters of the answers.
I was at a professional shop with in the last month, Having a tire fixed. And they recharged a persons a/c with the old shake and bake can, And didn't even pull a vac. I asked about a vac. and the kid told me about the same thing about the oil obsorbing the moisture. I will not be getting my a/c serviced there for sure....

That sounds like the Saturday morning mechanic's in front of the parts store with the cheap can tap set ups putting can after can of refrigerant in some old heap, so that it will be "extra cold"...

 

[royesses]

For anyone who needs/wants to learn more about charging-recharging automotive AC systems the following link is very good.
http://aircondition.com/tech/

" bought this one - http://www.harborfreight.com/25-cfm-...ump-61245.html $80 with a coupon. The best I could get was ~25 in Hg. Oh yeah - I'm at 4,912' ASL. "

At 5,000 feet elevation you need to add 5" Hg to get the equivalent reading at sea level.
So if I read you right your vacuum pump is doing great. If not please excuse my ignorance. I suffer from oldtimers disease.


"You also need some pretty good fittings and hoses to get down below 500 microns.

A lot of the problems people have getting that low is setup related vs pump related. "

Very true. I find many hoses leak at the connector due to no insert in the hose seals. Tighten the hose fittings and the seal crushes and blocks the passage to the manifold and deforms to allow air in. Also when charging with refrigerant this prevents the system from getting any charge. Robinair and others sell the inserts to fix this. On my personal vehicles I usually try to get down below 500 microns.
Roy

 

[2mJps]

What about useing a old compresser from a frig or window unit.

 

[royesses]

What about using a old compressor from a frig or window unit.

The first vacuum pump I purchased from Snap-On was based on a sealed unit from a refrigerator. They will work for that but a rotary vane two stage is capable of a higher vacuum. I used the Snap-On for years with no problems or come backs.

 

[JKady]

Great info, Thanks for posting the question to the op and thanks for the education to the posters of the answers.
I was at a professional shop with in the last month, Having a tire fixed. And they recharged a persons a/c with the old shake and bake can, And didn't even pull a vac. I asked about a vac. and the kid told me about the same thing about the oil obsorbing the moisture. I will not be getting my a/c serviced there for sure....

Bet the EPA would be very interested in how they're evacuating A/C systems if there's no machine in the shop.

 

[rayh91]

I have one of those vacuum pumps from HF. Wouldn't recommend it. Don't think it pulled anywhere near 20inHg. Only used it once or twice though but hey, it's cheap enough to try.

 

[Dagny]

Will autozone rent out a micron gauge along with the pump? If so thats what I would do I think almost all AC shops that have the recycling or reclaiming machines will put more contaminates in your system than they remove. Think of the variety of **** that can come out of the last 200 cars that came in R 12,22,502,134a,404a,propane, hot shot leak sealers,PAG POE AB AND all kinds of mineral oil, yikes.

 

[royesses]

Will autozone rent out a micron gauge along with the pump? If so thats what I would do I think almost all AC shops that have the recycling or reclaiming machines will put more contaminates in your system than they remove. Think of the variety of **** that can come out of the last 200 cars that came in R 12,22,502,134a,404a,propane, hot shot leak sealers,PAG POE AB AND all kinds of mineral oil, yikes.

Looked up that question (interesting question I've never thought of) here's what is on their web site, no micron gauge listed:

The Vacuum Pump is used for removing moisture and checking for system leaks. The use of a vacuum pump is often an overlooked step when performing the complete job. Applying a vacuum for 45-60 minutes will accomplish two things: removing moisture and checking for leaks.
The ability of the system to reach and maintain a state of vacuum is a sign that the system should be leak free. If the system is unable to reach 29 in/Hg (inches of mercury, the unit of measurement used when measuring vacuum) of vacuum, or the vacuum fails as soon as the pump is turned off, a leak probably still exists in the system.

The pump is available from AutoZone through the AutoZone Loan-A-Tool program.


That mix of refrigerants is a hell of a cocktail. Especially the sealants in the mix. I'll bet the shop owners just love those expensive machines getting slugged with that ****.

 

[Skin]

I'll be "that guy". If this is for your personal vehicle just go to a proper shop that has a recovery, recharge machine. Its less than $100 and you'll know its done right. All too often weekend mechanics vent the old refrigerant into the atmosphere and/or charge a system incorrectly AND without first checking for leaks or malfunctioning components. Only my opinion but they really shouldn't be offering recharge in a can to the general public.

 

[Dave88LX]

Learning what's needed to service my auto A/C stuff. Need a vac pump. Where would I get a micron gauge, what's recommended, and where would it connect?