Chevrolet Light Duty Truck 1973, Service Manual

Page: 66 / 979

1A-40 HEATER A N D AIR C O N D IT I O N I N G
• Cylinders or disposable cans should never be
subjected to high temperature when adding
refrigerant to the system. In most instances, heating
the cylinder or can is required to raise the pressure
in the container higher than the pressure in the
system during the operation. It would be unwise to
place the cylinder on a gas stove, radiator or use a
blow torch while preparing for the charging
operation, for a serious accident can result.
Remember, high pressure means that great forces
are being exerted against the walls of the container.
A bucket of warm water, not over 125°F, or warm
wet rags around the container is all the heat that is
required.
• Do not weld or steam clean on or near the system.
Welding or steam cleaning can result in a dangerous
pressure buildup in the system.
• Discharging large quantities of R-12 into a room
can usually be done safely as the vapor would
produce no ill effects; however, in the event of an
accidental rapid discharge of the system, it is
recommended that inhalation of large quantities of
R-12 be avoided. This caution is especially
important if the area contains a flame producing
device such as a gas heater. While R-12 normally is
nonpoisonous, heavy concentrations of it in contact
with a live flame will produce a toxic gas. The same
gas will also attack all bright metal surfaces.
• Protection of the eyes is of vital importance! When
working around a refrigerating system, an accident
may cause liquid refrigerant to hit the face. If the
eyes are protected with goggles or glasses, no serious
damage can result. Just remember, any R-12 liquid
that touches you is at least 21.7°F below zero. If
R-12 liquid should strike the eyes, here is what to
do:
1. Keep calm.
2. Do not rub the eyes. Splash the affected area
with quantities of cold water to gradually get the
temperature above the freezing point. The use
of mineral, cod liver or an antiseptic oil is
important in providing a protective film to
reduce the possibility of infection.
3. As soon as possible, call or consult an eye
specialist for immediate and future treatment.
PRECAUTIONS IN HANDLING
REFRIGERANT LINES
CAUTIO N:
The following precautions should
be observed when handling refrigerant lines:
• All metal tubing lines should be free of kinks,
because of the restriction that kinks will offer to the
flow of refrigerant. The refrigeration capacity of the
entire system can be greatly reduced by a single
kink.
• The flexible hose lines should never be bent to a
radius of less than 10 times the diameter of the
hose.
• The flexible hose lines should never be allowed to
come within a distance of 2-1/2" of the exhaust
manifold.
• Flexible hose lines should be inspected at least once
a year for leaks or brittleness. If found brittle or
leaking they should be replaced with new lines.
• Use only new lines that have been sealed during
storage.
• When disconnecting any fitting in the refrigeration
system, the system must first be discharged of all
refrigerant. However, proceed very cautiously
regardless of gauge readings. Open very slowly,
keeping face and hands away so that no injury can
occur if there happens to be liquid refrigerant in the
line. If pressure is noticed when fitting is loosened,
allow it to bleed off as described under "Purging the
System" in this section.
WARNING:
Always wear safety goggles when
opening refrigerant lines.
• In the event any line is opened to atmosphere, it
should be immediately capped to prevent entrance
of moisture and dirt.
• The use of the proper wrenches when making
connections on "O " ring fittings is important. The
use of improper wrenches may damage the
connection. The opposing fitting should always be
backed up with a wrench to prevent distortion of
connecting lines or components. When connecting
the flexible hose connections it is important that the
swaged fitting and the flare nut, as well as the
coupling to which it is attached, be held at the same
time using three different wrenches to prevent
turning the fitting and damaging the ground seat.
• "O" rings and seats must be in perfect condition. A
burr or piece of dirt may cause a leak.
• Sealing beads on hose clamp connections must be
free of nicks and scratches to assure a perfect seal.
MAINTAINING CHEMICAL STABILITY IN
THE REFRIGERATION SYSTEM
The metal internal parts of the refrigeration system and
the refrigerant and oil contained in the system are
designed to remain in a state of chemical stability as
long as pure R-12 and uncontaminated refrigeration oil
is used in the system.
However, when abnormal amounts of foreign materials,
such as dirt, air or moisture are allowed to enter the
system, the chemical stability may be upset. When
accelerated by heat, these contaminants may form acids
and sludge and eventually cause the breakdown of
components within the system. In addition, contaminants
may affect the temperature-pressure relationship of R-12,
LIGHT DUTY TRUCK SERVICE MANUAL