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Super Moderator
10,660 Posts
Discussion Starter · #1 · (Edited)
As it is getting close to the time when folks need a/c is a running dialogue that I had with Thomas Covenant, on a different forum.

Thomas it was really rather easy. I took the receiver/dryer out,
poured out the oil in it then I took the compressor off and poured
the oil out of it.

Filled the compressor with the proper quantity of pag oil, Replaced
all the o-rings that I broke the connectors on with nitrite rings.

Replaced the Condenser (salvaged from a wrecking yard, at 15 bucks
easier to take.

Then (here is where the nay-sayers are going to balk.) Placed on
the converter fittings and Placed one can of freon (r134a) in the

Then I went to the high pressure side of the condenser (engine not
running yet) and loosed the fitting till freon rushed out, for 10 seconds
then re-tightened. ( be careful not to get frost bite ). Wait 2 minutes for the
system to equalize. I started thecar, on the suction side placed a o-ring sealer in it,
then added a can or 134a. Turned on the a/c and it engaged the
compressor and sucked that can dry. I then topped it off with the
proper amount of r134a that it used for r12. Now the nay sayers
will tell you to draw vacuum, but I am a cheap bastard ( cost
effective) and was taught shade tree a/c from a friend. Bleeding
the high pressure side forces the high side to have hi pressure,
the low suction side then has low pressure, and you have then purged
all the lines of huh? So that when you kick it on, it
will suck in that can of freon like it should.....

Buying the kits will get you half the way there, but on my eagle I
had to use a high pressure adapter on the low side (only fitting
that would work) then buy a manifold kit and it comes with an
adapter and a gauge that connects to the High connector and then
allows you to place a can of Freon on it. The Two biggest problems
that I have seen happen with those kits, is that the compressor gets
too much oil. Draining the oil out of the Dryer, and the Compressor
and re-filling it with the proper amount of Pag oil is paramount to
getting a quiet and smooth running operation. I never buy the oil
charge, as I have filled the thing with the correct amount. Dupont
makes a Yellow can of leak detector, that you can see with uv
light. Most of the Cars I converted were because of a leaking
compressor 2 holed condenser and a compressor that locked up.

now for the ECO-Nazi's You should have your freon r12 sucked out by
a quality it has been known to damage the O-Zone ( my Ass)
layer. Like cow Flatuance, Mt Penetobo, Mt St. Helens didn't
either, but I didn't see the Eco-Nazi's fining Mother Nature. But
if your system is devoid of r12 by a broken condenser, loose fitting
(wink wink)then there is no problem with inserting the r134a instead
of r12, just remember that you need to drain all the oil out you
can. Run the a/c at max and if the lines don't sweat after a few
minutes then you need more freon, the other side of the coin is that
when the line starts sweating, your system has enough freon to do
the job. But personally I prefer the weighted method.

You will get all kinds of nay sayers and God-who-knows-it-alls, but
these are the steps that I followed, and they worked for me.

The Low pressure side where I put the convertor on.

The receiver dryer, that I removed to drain all the oil.

Under the washer jug

Closeup of the low pressure side

pic of the High pressure side I bleed the 134a on it is to the front of the radiator hose nipple.....

pressure test

low side 15 to 30
High side 150-270 up to 84
high side 150-210 from 85 up to 93

r209 compressor 79-81 10.0
sc209 compressor 79-81 8.0
Sankyo compressor 79-81 6.0

sankyo/sanden 10.0
york sc-209 8.0

85-89 6.0

90-93 4.8


80 2.06 pounds
81-84 2.0
85-91 2.5
92-93 2.06

I would assume that 92's lower poundage is due to r134 being installed.....but I can't verify that for a fact.

I went by the weight of the can for the total poundage that I was putting in then verified it by pressure/sweating test.

I have since purchased a Vacuum pump, and a good set of Manifold gauges, and using them properly takes a bit, but the end result is about the same.

56 Posts
Thanks for posting this info! I am going to need to fix my A/C on my '82 and this info will help me with the conversion.

346 Posts
If the original sticker is there with the correct R-12 charge amount use the formula R-134a=R-12x.9 -.5. (ie 2lb R12=1.3lb R134a) I work as a caddilac tech and do a LOT of AC work here in SC. R-134a pressures and amounts are different but it is the rational difference between the high and low sides of the system that malkes things happen. Dryer replacement is a good thing but not absolutly necessary unless the system has been open for a while. Either way I highly reccomend having you local trusted mechanic vaccuum the system to be sure all the moisture is out. Water and pag (or ester )oils like to eat all of the rubber like composites in the ac system. Talk to any ford guy about the 'black death' it's not pretty.
Stay cool.

72 Posts
i was thinking about doing this and i came across conversion kits, soo i see in your post that it says nothing about changing the parts other than the condenser? no need fo rnew seals and such?

Super Moderator
10,660 Posts
Discussion Starter · #5 ·
That is correct, I usually just replace the seals that I break. It was thought that earlier that if you were changing from r12a to 134a you would have to break everything loose and replace all of them. I never found this to be an issue.

I will tell you that if you change the drier out, (under the windshield washer) and drain the oil out of the compressor and fill it with the proper amount of rag oil, then reconnect the lines, and draw a vacuum, it will drastically help you in keeping the a/c producing the coolest air you can. I have had to change a couple of compressors lately, with driers, and have purchased a vacuum pump. I think it was like 129 at harbor freight, with it on sale for 100 with a 20 percent off coupon, so it wasn't that much. I tell you the difference is night and day.

Super Moderator
10,660 Posts
Discussion Starter · #8 ·
No, if yours isn't leaking or broken, there is no need to, it just so happens that I have had 3 bad condensers in my bunnies
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