R134a in '89 100Q unmodified

[dhowitt@iddis.com]

A number of you asked me to elaborate on how is it that I have
R134a in my '89 Audi 100Q, without modifications.  Sorry for the
delay in answering.  Here's my story. 

In preface, let me say that I'm a layman in this matter and I
look forward to any additional insights that Quattro list
members can provide on the technology involved.  All I know,
apart from what's below, is that it works for now. 

I bought the car from a gentleman, let us call him Mr. D., who
works for Elf-Atochem, a French chemical company that has
facilities in the Philadelphia area.  They manufacture
refrigerants, among other things.  A couple of years ago, as an
experiment, they asked employees to volunteer their cars for
conversion to R134a, and he volunteered this Audi.  

This was not a retrofitting process.  That was the whole point
of the experiment.  No parts were changed, as I understand it. 
They simply emptied the R12, "dried out" the system, and
refilled it with R134a & PAG lubricant. One must be careful not
to mix R134a and R12 because some sort of nasty things will
happen if you do.  They stuck a prominent warning label in the
engine compartment announcing that it contains R134a.

The results of the experiment are that it was found to work fine
for many cars, Mr. D. said, and mine is evidence in support of
that.  He also cited some studies confirming these results
published by the Mobile Air Conditioning Society (MACS) although
I haven't seen them.  I tried asking MACS about it and received
their current party line that one must replace the seals etc. to
convert, but apparently there are degrees of need for that, as
follows.

As far as I know there are two main problems associated with
dumping R134a into a system designed for R12.  Let me address
what I know about each.

First problem:  R134a molecules are smaller than R12 and thus
will leak out of a system engineered for R12.  Maybe, says Mr.
D., but it depends on the particular system and its condition. 
Many late-model cars can contain the R134a satisfactorily, he
reports.  Even if it leaks out slowly, it's a simple matter to
recharge it with R134a which you can buy in small cans at an
auto parts store -- as opposed to R12, which in the USA is now
illegal sold in end-user quantities.

I would add, from my own knowledge of AC systems, that to keep
one in good condition it is important to run the AC regularly so
that the lubricant that circulates with the refrigerant can keep
the hoses and seals coated internally.  If you leave your auto's
AC off for 8 months, chances are the hoses/seals will dry out &
crack, and it will leak the next summer, no matter which
refrigerant.  For this purpose, it is beneficial if your car
automatically turns on the compressor for de-humidifying when
running the defroster -- that keeps it exercised in winter
without your thinking about it.  My 100Q's automatic climate
control does that -- also my '91 Sable which has the climate
control option!

The other potential problem I've heard about is that R134a is
less efficient that R12, so it may provide less cooling effect
given the same size AC system.  Maybe so, but I'm getting air
out of the vents that measures 45F degrees, which is to spec, an
Audi mechanic told me.  In the recent (July '95) heat wave on
the U.S. east coast, I did plenty of driving with midday sun
beating in, outside temperatures near 100F, and high levels of
humidity, and I was kept plenty cool -- even had to turn the fan
to low as usual because it gets too cold (I actually have been
wondering if my thermostat is working right).  Its my
observation that most car AC systems are overpowered anyway, so
maybe one wouldn't notice a decrease in efficiency even if it
were so.

I've only had the car since March '95, but through a warm spring
and half of a hot summer I have had no problem.  As far as I
know the car has been running R134a for at least two years.  It
does emit a whining noise when the compressor is on -- I assume
this is normal but perhaps some of you could comment on that. 
(The belts are all new.)  

On the warning label in the engine, Elf-Atochem provided phone
numbers of people to call with questions about what they did,
but so far I've not had reason to call.  Perhaps some of you
from the Quattro list would want to suggest some questions or
issues to raise with them.  If so, I'll collect all the
questions, see what more they say, and report back.

Doran Howitt  
IDD Information Services  
Livingston, New Jersey
dhowitt@iddis.com