Subject: Re: Conversion to R-123A on My 1991 20V Turbo

[Joshua Van Tol]

The vacuum pump is 100% necessary if you want things to last very long and
perform well. Yes the system will "work" if you don't evacuate first, but
it will work less well than it should because of two things.
1.) You will have some air in the system, air is not compressible, and will
raise system pressures, which reduces efficiency, also it puts extra stress
on the hoses, compressor, etc.
2.) The moisture that's left in the system will cause problems. The drier
only has limited capacity to absorb moisture.

You can buy a nice vac pump for less than $200 these days. Don't get one of
those air powered venturi types, they do not work well enough to be worth
the effort. Someone also mentioned that some parts stores will rent them
for cheap or free.

I've found my investment in tools to be well worth it over the years. I
have a 134a gauge set, vac pump, can tap, and leak detector. Worth the
price of admission in my opinion.

Josh


On Tue, Jul 2, 2013 at 8:41 AM, Tony Hoffman <auditony at gmail.com> wrote:

> Also, if the compressor blew up, you will need to replace the expansion
> valve/orfice tube. They typically get plugged with metal shavings. I've
> never had any issue with a condensor plugging up due to a blown compressor.
> We do back flush everything when a compressor goes bad.
>
> If this was on the V8, consider yourself lucky. The Condensor design is
> larger and more efficient than the I-5 type 44's. Still serpentine flow,
> though. Just did a conversion on one (1989 100), 55 degrees at idle at
> 90deg ambient temp. 48 going down the road. I'd suspect that will rise to
> 65+ at idle when the temp goes above 100.
>
> You don't "need" the fittings for R134, you can charge an R12 car with the
> complete R12 guage set. BTDT. If you are using the small cans, get a side
> can tap, and there is no need for an adapter.
>
> The vacuum pump is used to evacuate the moisture out of the system. Not
> 100% necessary, but a very good idea.
>
> R134 fills to 80% of R12 capacity. So, if your car took 2lbs, multiply by
> .80, and you will use 1.6 lbs of 134.
>
> Yes, I feel I've had to learn way more than I ever wanted to about A/C
> since moving to TX :(  Five cars at the shop right now for A/C work.
>
> Tony
>
> On Mon, Jul 1, 2013 at 2:46 PM, Mike Arman <Armanmik at earthlink.net> wrote:
>
> Just did an A/C repair on another car . . . here's what I learned.
>
> 1) Everyone will tell you that your old R-12 gauge set isn't good for
> R-134, see, the fittings are different, and we have a new set for only
> $(fill in the blank).
>
> You can buy an adaptor set from fleabay for about $20. There's an adaptor
> for the red hose and one for the blue hose, they screw onto the hoses and
> have the correct R-134 snap fittings. You also need an adaptor for the
> yellow (supply) hose - I paid $5.00 including freight for that one, so for
> $25 I had an R-134 gauge set which I can still use on my R-12 car and R-22
> home A/C, etc.
>
>
> 2) Everyone will tell you that you need to buy a vacuum pump. Advance Auto
> will "rent" you one for $0.00 for a month. You put it onto a credit card
> and if you can get it back to them inside of a month, you get a full
> refund. If you are late, you get to keep it ;-) but alas, they'll keep the
> money.
>
>
> 3) Everyone will tell you that you need a new condenser. This is true if
> the old compressor has grenaded because sometimes you can't clean the
> condenser out (won't back-flush). If the system was working properly or
> just leaked out but didn't fail spectacularly, you don't need to buy this,
> keep the money.
>
> 4) You DO need a new receiver-dryer. These scavenge any residual moisture
> from inside the system. Best place I have found is Rock Auto, after
> shopping VERY carefully. Mine listed at over $100 from the stealer, $60 at
> FLAPS, $11 from Rock Auto - fits and works perfectly. Comes in a generic
> white box . . . I can live without a pretty box seeing that I'm just going
> to throw it away when I'm done anyway.
>
>
> 5) READ and UNDERSTAND the various instructions. They are poorly written,
> vague, imprecise and misleading. Better yet, get two or three instruction
> sets and compare them. There is a series of steps which must be done in
> order, and the various valves on the gauge set must be opened/closed in the
> correct sequence or you risk blowing the compressor. (Don't feed liquid
> freon to the high pressure side, kaplooie, don't open both valves on the
> gauge set simultaneously during the charge sequence, the only time they are
> both open is during the vacuum process.)
>
> 6) Don't overfill the system - more is not better. There's a specification
> somewhere (mine was 22 ounces) and of course each can has 12 ounces in it.
> You can do this with a scale (weigh an empty can, compare with a full one
> to determine the weight of the freon in a new can), or be content to
> underfill slightly (worked for me).
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