Chevrolet 10 Series 1968, Service Manual

Page: 45 / 713

HEATER AND AIR CONDITIONING 1A-14
• When filling a small drum from a large one, never
fill the drum completely. Space should always be
allowed above the liquid for expansion. If the drum
were completely full and the temperature was in­
creased, hydraulic pressure with its tremendous
force would result.
• 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 con­
tains a flame producing device such as a gas heater.
While R-12 normally is nonpoisonous, heavy con­
centrations 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 you can touch or that touches you is
at least 21.7°F. below zero. The eyeballs can't take
much of this temperature. If R-12 liquid should
strike the eyeballs, 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 tem­
perature above the freezing point. The use of min­
eral, 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.
REMEMBER - “ An ounce of prevention is worth a
pound of cure.”
PRECAUTIONS IN HANDLING REFRIGERANT LINES
• A ll metal tubing lines should be free of kinks, be­
cause 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 sealed lines from parts stock.
• When disconnecting any fitting in the refrigeration
system, the system must first be discharged of all
refrigerant. However, proceed very cautiously r e ­
gardless of gauge readings. Open very slowly, keep­
ing 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 very slowly.
CA U TIO N : 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 con­
nections 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 con­
nections 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 dif­
ferent wrenches to prevent turning the fitting and
damaging the ground seat.
• “ O” rings and seats must be in perfect condition.
The slightest 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 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
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 ac­
celerated by heat, these contaminants may form acids
and sludge and eventually cause the breakdown of com­
ponents within the system. In addition, contaminants may
affect the temperature-pressure relationship of R-12,
resulting in improper operating temperature and pres­
sures and decreased efficiency of the system (fig. 25).
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 moisture-free as it is
F ig . 25—System Contaminants
CHEVROLET TRUCK SERVICE MANUAL