AC recharge R12 to R134?

[ScottyCBoy at aol.com]

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In a message dated 6/6/2002 10:19:34 AM Central Daylight Time,
dsinclair at icare.snalf.com writes:


> The "hoses and compressor" parts are what I was concerned about.  My guy
> claims the compressor and hoses can stay with no detriment.  Do you think
> that the old compressor will deteriorate and croak over time if not changed
> out?  My recollection is that a compressor for the CoupeQ 20v isn't a cheap
> unit...?  I'd like to save some cash on the R-12, but if I have the car for
> three more years or so, I charge it once with R-134 to save $50, and have
> to buy a new compressor and have it recharged, I probably would have been
> money ahead to pay $100 a pound for R-12 and do a single charge of it,
> right?  Assuming I can find R-12 for any price that is...

You should be safe using the old hoses, you might experience a gradual loss
of R-134a over time though. On every 5000 I have converted I went with the
original compressor, I've had two start leaking at the shaft seal and one ate
itself to bits after three months. At one time High Low auto parts had a
rebuilt NP17C compressor for 160 dollars or there abouts. I have used this
compressor on my daily driver for almost two years with no problems. Although
these are kits out there that claim that all you have to do is add oil and
134a and your good to go I would recommend at a minimum do the following:

For type 44 cars:

Fix whatever problem you had with the A/C to begin with. Any problems that
are already there will be exasterbated with the new refrigerant.
Change All O-rings
Change Drier with one compatible with 134a, if the R-12 drier is used there
is a good chance that 134a will break down the dessicant and cause the
compressor to eat itself to bits.
Flush all old oil out of system
Change Orifice Tube

Use a quality oil Compatible with 134a. I always use Texaco Capella, it's a
synthetic oil that works excellent. I always add an extra few ounces of oil.
I read a study once with a lincoln continental, a group did to see how excess
oil will effect a system. they stopped at 30 ounces of oil and there was no
performance degredation of the system. Any extra oil will simply accumulate
in the drier, condensor, and evap.
Install r-134a type fittings.
Evacuate for a few hours
Fill with R-134a oil.

You might also have to do the following:

REplace hoses (not too hard to do on a type 44)
Replace compressor (inexpensive quality rebuilds can be found for the
Nippondenso unit).
Install a secondary fan over the condensor if high pressure is too high.
(Audi's in General have excellent condensors, very large, and high flowing.
I've never had to replace a condensor in a type 44 due to improper cooling.
(I have replaced some damaged ones though)

Scott