R12 Replacement

["R. Cummings" <cumm@flash.net>]

There is no drop in replacement for R-12. There are a number of vendors
trying to cash in on the potential millions to be made with R12
replacements. However, to date, Every vehicle manufacturer in the world
doing business in the U.S. recommends replacement ONLY with R134a.

A replacement for R12 must be on the EPA's SNAP list. An "approved"
replacement means that the chemical is ok environmentally - it does not mean
it will work. Go to www.epa.gov search using the word "SNAP" and you can get
a list of approved suppliers and chemical composition and a lot of other
information.

R12 and R134a are single component chemicals. The other replacements on the
list are blends. Repair shops today have 2 refrigerant recovery, recycle
machines, one for R12 and one for R134a. The general procedure is to recover
the refrigerant, clean it, repair the system and put the refrigerant back
it, along with an additional amount to make up a full charge.

Each chemical on the SNAP list must have its own unique fittings and must be
extracted from the system with a unique recycle machine but they cannot be
charged back into the system. The reason is that the various components of
blends leak at different rates, and extract at different rates so one never
knows what the composition is. Most of the blends contain a small amount of
butane to carry the oil in the system but not enough for the mixture to be
explosive.

Replacement refrigerant is a market place issue right now. But if 4 or 5
chemicals make a significant in-road in the market, a repair facility will
need 4 or 5 new machines to recover the different refrigerants (venting is
illegal). This cost will be passed on to the consumer or there may not be
anyone to service a particular refrigerant in the town you live in. 

Beware of smuggled R12. There is a lot of it around and since it is being
smuggled by criminals it should not be a surprise that a lot of it is
contaminated or a different product altogether. The fines for smuggling R12
are staggering but so are the profits.

Companies have also been trying to sell mixtures of propane and butane as a
"drop in refrigerant". It actually works fine but it turns your car into a
bomb. It is illegal to use explosive refrigerants for mobile A/C applications.

By the way, flushing does not use up refrigerant, so it will not drive the
price of a repair up.

We felt the change from R12 to R134a was going to be extremely difficult.
R134a is a smaller molecule than R12 and will leak out of smaller holes, so
barrier hoses were developed with a material layer to keep the refrigerant
in and a different material layer to keep the moisture out.

On the OEM level the change has gone easily with very few problems. In
addition, we have done conversions on company cars and personal cars and
have been amazed at the lack of problems.

Someone else mentioned the most important consideration when converting.
Make sure you solve the problem that led to the system not functioning with
R12. Once that is fixed, conversion is as easy as replacing the accumulator
(CCOT systems) or receiver/dryer (TXV systems). Add the recommended amount
of Ester oil and charge by weight to 90% of the recommended R12 charge.
Assuming the system was fairly clean you do not have to flush or remove the
mineral oil. Service fittings must be changed and a label must be placed on
the system. All this can be obtained from the A/C parts supply houses.

Even though the old hoses should leak with R134a, apparently the saturation
with mineral oil keeps the R134a in after these "dirty" conversions. If you
want, a lot of the supply houses will take your hose assemblies and using
the old metal fittings replace the hose with barrier hose.

One disadvantage of R134a is that it will run about 20 psi higher on the
high pressure side of the system compared to R12. If your car has condensing
problems and runs high head pressure you might have trouble. An aftermarket
fan in front of the condenser is the normal cure for this.

BTW the old York compressor is still being manufactured by a company named
CCI in Decatur, Ill. 217-422-0055. It is a two piston design that is noisy
and shakes a lot but is very rugged. It is used on more than half the large
tractor trailer trucks in the U.S. that run over 150,000 miles a year. There
are lots of rebuilders out there for this compressor.

So, thre moral of this long story is: use R12 until the costs get higher
than converting to R134a, then convert.

Bob Cummings
87 Coupe GT R12 but close