Chassis AC Service--Things You Should Know

[mrdonut12]

Before any refrigerant is added to your chassis AC system (dash
air), the system should be tested for purity of refrigerent
in it and also for the presence of air.
Some systems may not have pure R134A or R12. I've found
R22 and propane in some systems.
The presence of air means there's also moisture in the system
in the form of humidity in the air. That's right, it only takes
a little tiny bit to be a problem.
Moisture in a refrigeration system turns into acid over
time. That's why vehicles develop leaks in the evaporator
and condenser. The acid literally eats holes in them.
This is the reason systems need to be pulled down to a
deep vacuum during a service. The vacuum causes the moisture to
boil and evaporate out.
Leaks on the low (suction) side of the system can allow
air to be sucked in.
If the system is low and refrigerant is added, oil should
also be added. Oil circulates with the freon to lubricate the
compressor. If freon has escaped, it only makes sense that oil
has, as well.
I've found a very good premium oil made by BG products. It
will work in either system.
Several years ago, we started adding 2 ounces of BG oil with
every service we did (when the system was low) and since then,
our replacement compressor sales have dropped to near zero.
A large capacity system like a Bird will take more oil than
that.
The majority of compressor failures isn't from wearing out,
it's plain lack of lubrication. Adding freon only makes the
unit cool. Sometime later, the compressor locks up. "Bad
compressor" is the phrase. "Lack of lubrication" is the
real answer.
So, if you're going to save money and service your system
yourself, take the above steps to be sure you really ARE saving money
over the long term.
George Witt
81 FC 35
Lincoln, Nebraska