Chevrolet 30 Series 1967 Service Manual page 42

HEATER AND AIR CONDITIONING 1A-14
MAINTAINING CHEMICAL STABILITY IN THE
REFRIGERATION SYSTEM
The metal internal parts of the Chevrolet refrigeration
system and the refrigerant and oil contained in the sys­
tem are designed to remain in a state of chemical sta­
bility as long as pure R-12 and uncontaminated refrigera­
tion oil is used in the system.
However, when abnormal amounts of foreign m aterials,
such as dirt, air or moisture are allowed to enter the
system, the chemical stability may be upset. When ac­
celerated by heat, these contaminates may form acids
and sludge and eventually cause the breakdown of com­
ponents within the system. In addition, contaminates may
affect the temperature-pressure relationship of R-12,
resulting in improper operating temperature and pres­
sures and decreased efficiency of the system.
The following general practices should be observed to
insure chemical stability in the system.
• Whenever it becomes necessary to disconnect a
refrigerant or gauge line, it should be immediately
capped. Capping the tubing will also prevent dirt and
foreign matter from entering.
• Tools should be kept clean and dry. This also in­
cludes the gauge set and replacement parts.
• When adding oil, the container should be exception­
ally clean and dry due to the fact that the refrigera­
tion oil in the container is as m oisture-free as it is
possible to make it.
sorb any moisture with which it comes in contact.
For this same reason the oil container should not be
opened until ready for use and then it should be
capped immediately after use.
• When it is necessary to open a system, have every­
thing you will need ready and handy so that as little
time as possible will be required to perform the
operation. Don't leave the system open any longer
than is necessary.
• Finally, after the operation has been completed and
the system sealed again, air and moisture should be
evacuated from the system before recharging.
GAUGE SET
The gauge set (fig. 23) is used when purging, evacuat­
ing, charging or diagnosing trouble in the system. The
gauge at the left is known as the low pressure gauge.
22 -
Fig . System Contaminants
Therefore, it will quickly ab­
Fig. 23 - G a u g e Set
The face is graduated into pounds of pressure and, in
the opposite direction, in inches of vacuum. This is the
gauge that should always be used in checking pressures
on the low pressure side of the system. When all parts of
the system are functioning properly the refrigerant
pressure on the low pressure side never falls below
pounds pressure. However, several abnormal conditions
can occur that will cause the low pressure to fall into a
partial vacuum. Therefore, a low pressure gauge is
required.
LOW PRESSURE
CONTROL
VACUUM
CONTROL
(3)
LOW
GAUGE LINE
24 - J-8393
Fig .
HIGH PRESSURE
CONTROL (2)
FREON
CONTROL
(4)
HIGH PRESSURE
GAUGE LINE
5 LB. CHARGING
CYLINDER
LEAK
DETECTOR
FREON DRUM
CONTROL VALVE
Charging Station
CHEVROLET TRUCK SERVICE M ANUAL
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