Message from Rodger B Carter
Subject: R-12 vs R-134a
=================
Hi all, Any suggestions to whether I should convert my R-12 system to R-134a
when Townsend Imports says they, 'We only convert systems when the compressor
fails and is being replaced' (see Ywan's message below) and my compressor is
still good?  (The cause of my leak is a lose hose crimp).

Also, if I stay with R-12 should I replace the Drier, the Expansion Valve,
and the O-rings while I have the 18 year old system in my 84900T open?
Thanks, 
Rodger 
Ywan on AC 
For any hoses except the gang off the 900 16V compressors, we make up the
lines with a set of non crimping fittings . These allow you to replace just
the rubber hose in the future should it go bad. We were introduced to them by
a customer who works for a hydraulic company. They consist of a sleeve that
is threaded onto the outside of the hose and then a tapered insert is
threaded into the inside of the hose and the sleeve. We use a nylon sleeved
barrier hose for the rubber section, compatible with any refrigerant/oil. The
fittings are available to fit to existing metal lines via compression
fittings. They also are available to fit flared compressors like the older 8
Vs use and can be had with any number of angles on them and in any diameter
on the cars. The hose gang off the compressor is $72, and with all the
fittings needed to reconstruct it, it is usually cheaper to just replace the
hose. The site has the fittings and hose we use most often with pricing. $420
for a single hose replacement, reciever drier ( if the system was totally
discharged or really old), expansion valve while you are there and evacuation
and recharge is high IMO. Driers are less than $30, expansion valves about
$25, the hose we make up initially is about $60 (then $10 if the rubber is to
be replaced). Freon is $38/lb (R1324a $6/lb). So exactly how much labor is
being charged?. Die tests are unnecessary with modern detectors, usually a
gimmick to sell you something at a mark up (the dye kit). A good shop will
have a MACS Yokogawa detector that will sniff out leaks as low as a .10
oz/year. On a completyely discharged system, the introduction of just a pound
of refrigerant will be enough pressure for the Yokogawa to find the leak(s),
there's no need to fully charge and then have to evacuate the system fully.
The Saab retrofit kit is not necesasary for the conversions. It's most
expensive component besides the reciever drier is a section of hose only
necessary if you purge the system by the procedure Saab outlines which calls
for continuous filling and evacuating of dry R12 until the system is clean.
This is time consuming and I have ran a test behind the procedure with
mineral spirits. Even after the R12 purge was carried out to the letter of
the bulletin, the mineral spirits still came out into a collecting bag with a
lot of debris and oil. The spirits are clear when they go in, and when they
came out, they were dark and carried a lot of fine particles. All you need
for a retro fit is a new reciever drier rated for R134a, $.30 o rings for
replacing the ones you disturb during the conversion, and R134a fittings for
gauges so it will be evident what refrigerant is in the system. A label is
advised, but not really necessary since the fittings will not allow R12
gauges to be fitted. We use high quality brass fittings and permanent brass
caps on the R12 fittings that will not be used on systems with extra ports.
For a 900, the reciever drier we use is made by Parker (same as in the Saab
kit) for $24.60 and about the same for a 9000. I just discovered that the
parts search is not up to date on these driers for the 9000. we now have a
Parker replacement for them at around $30, but the parts search is not
showing it, nor is my inventory here at home. I'm not sure why, but will
remedy the situation on Monday. Buying the parts you need individually
instead of a kit with stuff you throw away included is a lot cheaper than
$100. The 9000 kit is a lot more than $100 too. The 9000 kit includes a
pressure switch for the drier that turns the fan on later than the R12
system, i.e. it lets the high side get even higher before it turns on the
auxillary fan. We keep the old switch in the systems we service and it keeps
the high side pressures lower extending the life of the system and providing
more cooling. So far, there has been no increased failure of the auxillary
fans. Saab compressors have Viton front seals. Viton absorbs R12 and the
mineral oil it uses. Converting to R134a without replacing the compressor is
not advisable, either the seal or the bearings in the old compressor will die
soon afterwards. We only convert systems when the compressor fails and is
being replaced. For the extra $50, we put on a new reciever drier and
expansion valve and flush the system with mineral spirits. Doing the full
procedure and carefully measuring the oil and refrigerant added has given us
results with the conversion that work just as well as the original R12,
center vent temps in the 38-42 degree range with pressures on the high side
not exceeding 225 psi.

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