Climate Control

R-134a Retrofit Bulletin

Before you buy that quickie-retrofit kit, read how Porsche retrofits A/C systems to R134a. The
TSB includes all part numbers required for each of the models covered. The TSB is 13 pages
long.

It is not that much more work to do your A/C retrofit to factory specifications.

Go To:
http://members.tripod.com/prsch944
SELECT: Porsche A/C
SELECT: TSB 89501 - Retrofitting R12 A/C System to Refrigerant R134a

F.R. Wilk
84 944 - Dark Gray/Black
80 924Turbo - Silver/Black - my parts car
85 944 - Garnet Red/Black - my other parts car


I just finished reviewing the AC SB concerning the R134a conversion, and was surprised to see
that all the seals do not require replacement.

Am I mistaken, or hasn't the general post been to replace all old seals as they are incompatible
with the new refrigerant?

A simple drier and fill-valve replacement sounds quite a bit more pleasant than a total seal
swap!

Marty
86.5 Indischrot 5-speed
356C


After doing the R12 -> R-134a conversion to my '89 S4, I figured it would be a good idea to at
least peek at the PCNA tech service bulletin to see if I missed anything. Thanks to F.R. Wilk for
pointing the way to that document online. The procedure they propose is somewhat simplistic,
and in my opinion incomplete. If you are considering making the move to R-134a from R-12,
think about the reason you are changing. It's probably because of a leak in the system
someplace, or poor system performance due to leakage sometime in the car's life. Maybe it's
because of some catastrophic compressor failure. No matter-- the TSB is targeted at vehicles
that are running perfectly on R-12, and only are changing because of the driver's green
conscience. Note that the TSB proposes a sweep with R12 to get more old oil out, so it includes
the cost of that extra 3lbs of gas, plus an additional recovery cycle. Not a bad idea, just a little
expensive compared with manually draining the compressor.

So-- Leak-check the system with a known good electronic gas sniffer before and after your
conversion. The o-rings in the couplings and components do tend to leak in their old age, and
there are plenty of them especially on M570 optioned cars (rear air conditioner). Fix any leaks
that you find, and consider replacing all those o-rings just to be sure. It adds a few hours to the
project, but gives you a fresh start with regard to system life.

Replace the expansion valve(s). Using the correct valves lets you get the best evaporator
performance with the R-134a gas.

The TSB recommends a Porsche-branded refrigeration oil they describe as ND-Oil 8. My local
Nippon-Denso service and supply operation in Long Beach recommends the polyolester

refrigerant oil for their equipment in R-134a service. Porsche's only description in the TSB is
that their oil is "of a synthetic type." It may be the ester oil in a fancier bottle. There are some
watchouts when using the ester oil, specifically with air and moisture exposure during the
conversion process. An interesting option for system oil fill is to "vacuum" the oil charge in
following the second evacuation, never exposing the oil to more than a few minutes of air
during the process.

On the TSB page for my '89 S4, the TSB recommends a straight low pressure adapter, and the
angled high pressure adapter. Most charge hose kits now come with right-angle
quick-disconnect fittings on the end of the hoses so, at least on this car, it makes sense to use
the angle adapter fitting on the low pressure charge port. Their recommendation for not
removing the existing schraeder valve core when installing the straight adapter does not apply
to the third-party adapters commonly available. Plan on removing the old valves when either
adapter will be installed.

dr bob