OT, but much more technical that the various spam postings of late.

I need to swap out the condensor & receiver/dryer on my wife's car
after a tube clip chaffed thru a condesor tube. I do not own a vacuum
pump (and did not think of searching Craigslist & e-Bay a couple of
months ago to buy a vac pump) and I have not found a local place to
rent one. I see very cheap (under $20 new) pneumatic pumps driven off
of shop air, about 4 CFM air use. Has anyone here have experience
using one of these? Do they pull a good vacuum ( I have seen
notations of drawing 27 inches Hg of vacuum). How long does one need
to run such a vac pump to draw a good vacuum? I realise I could just
take the car to an A/C service place and have them recharge, but I
will be adding A/C to a couple of project cars next year and owning an
vac pump could pay for itself.

I have a set of R12 A/C manifold gages. I think that there are
adapter fittings to convert this over to a 134A use. Anyone have
experience in using the adapters?

I see very cheap (under $20 new) pneumatic pumps driven off
of shop air, about 4 CFM air use. Has anyone here have experience
using one of these? Do they pull a good vacuum ( I have seen
notations of drawing 27 inches Hg of vacuum).

That will do just fine, if you add a refrigerant backfill to "rinse" the
system and repeat the rough vacuum. With a pure backfill gas and enough
repeititions, your rough vacuum is as good as a hard vacuum at removing
non-condensibles, which is the point. Indeed, with rinsing you don't
even need a vacuum; the vacuum just decreases the number of rinses
needed to achieve a target purity inside the system. Backfilling and
rinsing is not strictly legal in some jurisdictions, but it's no
different from shooting a few ounces into a leaky system to test for
leaks.

There's a superstition amongst A/C techs that pulling a 50 micron vacuum
is needed to "boil off" moisture from the dessicant. In fact, no vacuum
will regenerate the dessicant. If the system has been contaminated, you
should replace the dessicant.

If you look at the OEM factory manuals for auto A/C back in the 1970s,
you'll see that before the recycling machines came into use for the
Clean Air Act in 1990s, that a very crude vacuum pump is what
*everybody* used. The authorized GM A/C vacuum tool from those days was
a small piston refrigeration compressor unit.

This sort of superstition is encouraged because the pros believe and
sell the idea that only they have the tools to do the job, which no
DIYer could reasonably afford. It also justifies the $5K they were
suckered into paying for a recycling machine.

Oh, for those days when you fixed your auto A/C hoses with tire patches
and hose clamps, went to K-Mart and bought an armful of R12 cans for
$1/each.

The Harbor Freight gadget is very inefficient and takes a lot of air
compressor CFM to run properly, more than most homeowner compressors can
deliver, but given that, it does work for a rough vacuum, plenty for
improvising A/C work.

How long does one need to run such a vac pump to draw a good vacuum?

Again this is typically governed by superstition. The point of the
vacuum is to remove non-condensible gases. Whatever vacuum you have
will do whatever it will do in a few minutes. But you'll find techs who
leave their $500 rotary-vane pump on there overnight, thinking it
somehow must be better.

Your effort is best spent on fixing leaks with a vacuum test. It is all
a waste of time if your system leaks in the slightest.

I have studied and worked on dozens of my own AC systems for 35 years,
and proved these improvised techniques many times.

On Thu, 24 Apr 2008 14:03:07 -0500, Richard J Kinch
wrote:

I see very cheap (under $20 new) pneumatic pumps driven off
of shop air, about 4 CFM air use. Has anyone here have experience
using one of these? Do they pull a good vacuum ( I have seen
notations of drawing 27 inches Hg of vacuum).

That will do just fine, if you add a refrigerant backfill to "rinse" the
system and repeat the rough vacuum. With a pure backfill gas and enough
repeititions, your rough vacuum is as good as a hard vacuum at removing
non-condensibles, which is the point. Indeed, with rinsing you don't
even need a vacuum; the vacuum just decreases the number of rinses
needed to achieve a target purity inside the system. Backfilling and
rinsing is not strictly legal in some jurisdictions, but it's no
different from shooting a few ounces into a leaky system to test for
leaks.

Not pulling a proper hard vacuum and then "rinsing" or "purging"
with refrigerant as you put it can cost you a minimum $50,000 fine.

You are Not Allowed To Vent Refrigerant to the Atmosphere Anymore,
PERIOD. They make a point to stress this when you get your
refrigerant technician license. It has to be recovered.

If you want to chance it yourself, go ahead. But don't be so
cavalier as to suggest that others do it without their being informed.

The pneumatic vacuum pumps are not effective enough to remove free
moisture from the system. You need a proper oil ballasted vacuum pump
to evacuate any refrigeration system.

And if the system has been open to the atmosphere for long periods
(zero-leak left open/empty for a year or two before fixing) or gotten
water inside, you have to change out the filter/drier.

-- Bruce --

wrote:
OT, but much more technical that the various spam postings of late.

I need to swap out the condensor & receiver/dryer on my wife's car
after a tube clip chaffed thru a condesor tube.
An alternative is to spend a half hour reading the info on line
and then take the on-line test for the EPA "green" card that
allows you to buy R-12 in small cans for vehile A/C service.
I paid $19 for mine, there's no expiration to renew. It might
cost more now, but still should be way cheaper than a conversion
of the whole system.

Jon

On Apr 24, 5:32*am, wrote:
OT, but much more technical that the various spam postings of late.

I need to swap out the condensor & receiver/dryer on my wife's car
after a tube clip chaffed thru a condesor tube. *I do not own a vacuum
pump (and did not think of searching Craigslist & e-Bay a couple of
months ago to buy a vac pump) and I have not found a local place to
rent one. *I see very cheap (under $20 new) pneumatic pumps driven off
of shop air, about 4 CFM air use. *Has anyone here have experience
using one of these? *Do they pull a good vacuum ( I have seen
notations of drawing 27 inches Hg of vacuum). *How long does one need
to run such a vac pump to draw a good vacuum? * I realise I could just
take the car to an A/C service place and have them recharge, but I
will be adding A/C to a couple of project cars next year and owning an
vac pump could pay for itself.

I have a set of R12 A/C manifold gages. *I think that there are
adapter fittings to convert this over to a 134A use. *Anyone have
experience in using the adapters?

You can use the adapters, they were fairly reasonable from online
sources. When I got my gauge set, R134 ones weren't readily
available, so I got an R12 set and the adapters. Can't help you on
the venturi unit, I'm using an old Welch lab pump with an adapter for
the manifold set. You might want to go through the whole system and
replace the O-rings. All of mine were hard as rocks, some
disintegrated when I tried to remove them. Beats having a charge leak
off in a couple of months. Cans of refrigerant aren't 69 cents each
like they used to be. There are some web sites that cater to auto A/
C, the bits and pieces are a lot are reasonable from them than the
local chain stores. Only place I was able to find a bearing for the
compressor clutch pulley was online, a whole lot cheaper than buying a
whole rebuilt unit.

Stan

wrote in message
...
OT, but much more technical that the various spam postings of late.

I need to swap out the condensor & receiver/dryer on my wife's car
after a tube clip chaffed thru a condesor tube. I do not own a vacuum
pump (and did not think of searching Craigslist & e-Bay a couple of
months ago to buy a vac pump) and I have not found a local place to
rent one. I see very cheap (under $20 new) pneumatic pumps driven off
of shop air, about 4 CFM air use. Has anyone here have experience
using one of these? Do they pull a good vacuum ( I have seen
notations of drawing 27 inches Hg of vacuum). How long does one need
to run such a vac pump to draw a good vacuum? I realise I could just
take the car to an A/C service place and have them recharge, but I
will be adding A/C to a couple of project cars next year and owning an
vac pump could pay for itself.

I have a set of R12 A/C manifold gages. I think that there are
adapter fittings to convert this over to a 134A use. Anyone have
experience in using the adapters?

1. I am not a refrig tech nor do I offer legal advice. That said:
2. I have had good luck just swapping over from R12 to R134 - put adapters
on the fittings add some proper oil and fill
3. I have had no problem with systems that were open to the air for a short
period of time - but it is dryer here than in some places - I have
repaired/refilled systems and then run them for ten years without further
problems after a burst hose
4. harbor freight has an inexpensive R134 manifold set - I think it's on
sale now - about $50


** Posted from http://www.teranews.com **

Bruce L. Bergman writes:

Not pulling a proper hard vacuum and then "rinsing" or "purging"
with refrigerant as you put it can cost you a minimum $50,000 fine.

Would that be for everybody buying a $6 can of R134a at Walmart, or just
EPA licensed professionals? Cuz there's a lotta federal felons if it's the
former. The store shelf is worse than a crack dealer's console?

The pneumatic vacuum pumps are not effective enough to remove free
moisture from the system.

Neither are the best vacuums. This is a coveted myth of the over-tooled
technician. Consider why free moisture exists in the vacuum of outer
space.

You need a proper oil ballasted vacuum pump
to evacuate any refrigeration system.

Let the fresh dessicant scrub the moisture. That's what it's for. The
vacuum is only done to remove non-condensibles.

Jon Elson writes:

An alternative is to spend a half hour reading the info on line
and then take the on-line test for the EPA "green" card that
allows you to buy R-12 in small cans for vehile A/C service.

While I would agree that this is worth doing, note that you have to own
several $1000s in tools (recovery systems, etc) to lawfully apply that
license to any actual work. Otherwise you're an EPA felon.

Thanks for the replys - not intending to get people riled up. I had
planned on taking it to an A/C shop to have it drawn down and
recharged but then I thought that since I need to do this again for
two more cars next year - I might as well look into buying a vacuum
pump and a set of 134A gages or adapter ends for my existing R22
gages..

This car is only 4 1/2 years old so it is already R134A from the
factory and I have already purchased the receiver/dryer along w/ the
replacement condensor. The tube clip chaffed thru the condensor tube
back in Nov or Dec. I'm a bit ****ed at myself for not thinking about
looking for a vacuum pump back in Dec/Jan/Feb.

I'm considering trying one of the pneumatic pumps from Harbor Freight
- if it does not work, I have 30 days to return it. My father has an
older A/C vac pump - but he lives on the opposite end of the country
from me.

In article ,
Bruce L. Bergman wrote:

Not pulling a proper hard vacuum and then "rinsing" or "purging"
with refrigerant as you put it can cost you a minimum $50,000 fine.

You are Not Allowed To Vent Refrigerant to the Atmosphere Anymore,
PERIOD. They make a point to stress this when you get your
refrigerant technician license. It has to be recovered.

Of course you could rinse & purge using propane; a small amount left in
is so similar to refrigerants that it is no problem

Free men own guns - www(dot)geocities(dot)com/CapitolHill/5357/

On Fri, 25 Apr 2008 07:28:36 -0500, nick hull wrote:

In article ,
Bruce L. Bergman wrote:

Not pulling a proper hard vacuum and then "rinsing" or "purging"
with refrigerant as you put it can cost you a minimum $50,000 fine.

You are Not Allowed To Vent Refrigerant to the Atmosphere Anymore,
PERIOD. They make a point to stress this when you get your
refrigerant technician license. It has to be recovered.

Of course you could rinse & purge using propane; a small amount left in
is so similar to refrigerants that it is no problem

Free men own guns - www(dot)geocities(dot)com/CapitolHill/5357/

Propane is a perfectly good refrigerant, in fact most gas separation
plants use propane as the refrigerant. It runs at different pressures
and temperatures then the "R" stuff but the systems work well.


Bruce-in-Bangkok
(correct email address for reply)

On Fri, 25 Apr 2008 04:53:15 -0700 (PDT), wrote:

Thanks for the replys - not intending to get people riled up. I had
planned on taking it to an A/C shop to have it drawn down and
recharged but then I thought that since I need to do this again for
two more cars next year - I might as well look into buying a vacuum
pump and a set of 134A gages or adapter ends for my existing R22
gages..

This car is only 4 1/2 years old so it is already R134A from the
factory and I have already purchased the receiver/dryer along w/ the
replacement condensor. The tube clip chaffed thru the condensor tube
back in Nov or Dec. I'm a bit ****ed at myself for not thinking about
looking for a vacuum pump back in Dec/Jan/Feb.

I'm considering trying one of the pneumatic pumps from Harbor Freight
- if it does not work, I have 30 days to return it. My father has an
older A/C vac pump - but he lives on the opposite end of the country
from me.

Check pawn shops, E-bay and Craigslist, and other sources for a used
vacuum pump. Unless it's been beat to death and the oil never
changed, they last.

The only differences between a R-12 and R-134 manifold is the Acme
QC hose fittings and the markings on the gauges - and the high side
goes higher. The one from Harbor Freight will work fine, but if you
don't trust them they run around $100 for a 'real' one.

It is possible to build your own recovery machine out of a good used
hermetic compressor and other spare pieces, but you have to have a
clue how to do it - in Eastern Europe where the Communist system meant
they simply could not buy refrigerant at any price before the Wall
fell, they've been recovering and reusing refrigerants for decades
with homemade gear.

And a recovery cylinder is a propane cylinder with a yellow over
grey paint job and a different valve.

-- Bruce --

On Apr 25, 1:34*pm, Bruce L. Bergman
wrote:
.

* Check pawn shops, E-bay and Craigslist, and other sources for a used
vacuum pump. *Unless it's been beat to death and the oil never
changed, they last.

* The only differences between a R-12 and R-134 manifold is the Acme
QC hose fittings and the markings on the gauges - and the high side
goes higher. *The one from Harbor Freight will work fine, but if you
don't trust them they run around $100 for a 'real' one.

* It is possible to build your own recovery machine out of a good used
hermetic compressor and other spare pieces, but you have to have a
clue how to do it - in Eastern Europe where the Communist system meant
they simply could not buy refrigerant at any price before the Wall
fell, they've been recovering and reusing refrigerants for decades
with homemade gear.


I actually looked up a couple of web pages on fabbing a vac pump from
a refridge compressor - I do not have time to play right now. I
started looking on E-bay (used Robinairs nearby selling for about
$160+) Nothing on Craigslist locally and a used tool emporium had
USED pumps starting at $260!!!.

nick hull writes:

Of course you could rinse & purge using propane; a small amount left in
is so similar to refrigerants that it is no problem

Yes, aside from the nuisance of the mercaptan odorants.

On Fri, 25 Apr 2008 12:49:11 -0700 (PDT), wrote:
On Apr 25, 1:34*pm, Bruce L. Bergman
wrote:

* Check pawn shops, E-bay and Craigslist, and other sources for a used
vacuum pump. *Unless it's been beat to death and the oil never
changed, they last.

* The only differences between a R-12 and R-134 manifold is the Acme
QC hose fittings and the markings on the gauges - and the high side
goes higher. *The one from Harbor Freight will work fine, but if you
don't trust them they run around $100 for a 'real' one.

* It is possible to build your own recovery machine out of a good used
hermetic compressor and other spare pieces, but you have to have a
clue how to do it - in Eastern Europe where the Communist system meant
they simply could not buy refrigerant at any price before the Wall
fell, they've been recovering and reusing refrigerants for decades
with homemade gear.

I actually looked up a couple of web pages on fabbing a vac pump from
a refridge compressor - I do not have time to play right now. I
started looking on E-bay (used Robinairs nearby selling for about
$160+) Nothing on Craigslist locally and a used tool emporium had
USED pumps starting at $260!!!.

New is around $300 for a decent 1/3 HP vacuum pump and $600 for a
small recovery machine in a big city with actual competition. Note
that you want to buy a case of vacuum pump oil and change it after
every use. (Or bi-weekly to weekly if it's getting used every day.)

You can spend more and get better (more features, all automatic) or
faster (higher HP) examples of each, but there is enough competition
between makers that they can't just charge whatever they want.

And you can build a decent recovery machine, but refrigeration
compressors don't generate a good enough vacuum for purging. You
really need a purpose built vacuum pump for refrigeration.

-- Bruce --

On Fri, 25 Apr 2008 19:43:30 -0500, Richard J Kinch
wrote:

nick hull writes:

Of course you could rinse & purge using propane; a small amount left in
is so similar to refrigerants that it is no problem

Yes, aside from the nuisance of the mercaptan odorants.


If you buy commercially pure propane it has no odorant in it. You are
thinking of cooking gas that has mercaptans added for safety.

In fact, most airosol cans use propane as a propellant these days.

Bruce-in-Bangkok
(correct email address for reply)

Bruce in Bangkok writes:

If you buy commercially pure propane it has no odorant in it.

That would seem a tautology.

What is a convenient source for this wondrously pure stuff? I know you can
buy cylinders from lab chemical suppliers, but that is quite pricey. Tap a
can of PAM?

Lotsa fun stories he

http://www.chemaxx.com/aerosol3.htm

Richard J Kinch wrote:
Jon Elson writes:


An alternative is to spend a half hour reading the info on line
and then take the on-line test for the EPA "green" card that
allows you to buy R-12 in small cans for vehile A/C service.


While I would agree that this is worth doing, note that you have to own
several $1000s in tools (recovery systems, etc) to lawfully apply that
license to any actual work. Otherwise you're an EPA felon.

Nope. The license apparently gives you the option of building
your own system, so I did. The only part I "cheated" on is not
having a NIST-traceable vacuum gauge to verify the system
pressure before opening it up. Well, in fact, the damn system
had totally leaked down to nothing by the time I got into it, so
there really was no refrigerant to extract. But, I went through
the rigamarole anyway, just to be legal.

I've never actually used the card for its intended purpose, as
the only R-12 car I have left is 17 years old and has never
leaked at all. One of those miracle Japanese-built Toyota
Corollas from 1989. But, I did need a run capacitor for our
house A/C last summer. I went to one of those closed-shop A/C
supply outfits, and they had the cap for something like $4.77
but didn't want to sell it to me until I showed them the EPA
green card! So, it paid for itself already! That cap would
have cost $50+ at a retail shop, if I could even have found it
anyplace else.

Jon

Jon Elson writes:

The license apparently gives you the option of building
your own system, so I did.

I believe you're required to have a recovery apparatus from a list of
approved commercial models. I squeaked by with buying one of the last
of the "Roger Ram" hand-pump versions back in the 1990s when they were
legal, which cost only $100s instead of $1000s for the cart systems. I
would dutifully use that to laboriously pump out the vapor into a
recovery tank that looks like a 20 lb propane tank, when I have R12
systems to work on. Not something you want to do every day.

I am not aware that you are allowed to roll your own in this regard. If
that were the case, I'd suggest a recovery tank in an ice bath.

I went to one of those closed-shop A/C
supply outfits, and they had the cap for something like $4.77
but didn't want to sell it to me until I showed them the EPA
green card!

Worth your while to lay in spare capacitors and contactors from eBay
instead of paying desperate retail prices. Or at least have Grainger
standing by.