Chevrolet 10 Series 1968, Service Manual

Page: 48 / 713

HEATER AND AIR CONDITIONING 1A-17
CHIMNEY
REACTION PLATE
BURNER HEAD
BURNER TUBE
PROPANE GAS
CYLINDER
SAMPLING TUBE
blue again. Observations are best made in a semi­
darkened area. If the flame remains yellow when
unit is removed from leak, insufficient air is being
drawn in or the reaction plate is dirty.
NOTE: A refrigerant leak in the high pressure
side of the system may be more easily detected
if the system is operated for a few minutes,
then shut off and checked immediately (before
system pressures equalize). A leak on the low
pressure side may be more easily detected after
the engine has been shut off for several minutes
(system pressures equalized); this applies par­
ticularly to the front seal.
AVAILABILITY OF REFRIGERANT-12
Refrigerant 12 is available through Parts Stock in 25
lb. drums and in 15 oz. disposable cans.
Normally, air conditioning systems are charged making
use of the J-8393 Charging Station which uses the 25 lb.
drum. Evacuating and Charging Procedures are noted
later in this section.
The 15 oz. disposable cans are generally used for
miscellaneous operations such as flushing.
F ig . 29—Leak Detector
3. Adjust flame until desired volume is obtained. This
is most satisfactory when blue flame is approxi­
mately 3/8” above reactor plate. The reaction plate
will quickly heat to a cherry red.
4. Explore for leaks by moving the end of the sampling
hose around possible leak points in the system. Do
not pinch or kink hose.
NOTE:
Since R-12 is heavier than air, it is
good practice to place open end of sampling tube
immediately below point being tested, particu­
larly in cases of small leaks.
CA U TIO N : Do not breathe the fumes that are
produced by the burning of R-12 gas in the de­
tector flame, since such fumes can be toxic in
large concentrations of R-12.
5. Watch for color changes. The color of the flame
which passes through the reaction plate will change
to green or yellow-green when sampling hose draws
in very small leaks of R-12. Large leaks will be
indicated by a change in color to a brilliant blue or
purple. When the sampling hose passes the leak,
the flame will clear to an almost colorless pale
INSPECTION AND
PRE-DELIVERY INSPECTION
1. Check that engine exhaust is suitably ventilated.
2. Check the belt for proper tension.
3. With controls positioned for operation of the system,
operate the unit for ten minutes at approximately
2000 rpm. Observe the clutch pulley bolt to see that
the compressor is operating at the same speed as
the clutch pulley. Any speed variation indicates
clutch slippage.
4. Before turning off the engine, check the sight glass
to see that the unit has a sufficient Refrigerant
COMPRESSOR OIL
Special refrigeration lubricant should be used in the
system. It is available in 1 quart graduated bottles
through Parts Stock. This oil is as free from moisture
and contaminants as it is possible to attain by human
processes. This condition should be preserved by im­
mediately capping the bottle when not in use.
See “ A ir Conditioning System Capacities” for the
total system oil capacity.
Due to the porosity of the refrigerant hoses and con­
nections, the system refrigerant level will show a definite
drop after a period of time. Since the compressor oil is
carried throughout the entire system mixed with the
refrigerant a low refrigerant level will cause a dangerous
lack of lubrication. Therefore the refrigerant charge in
the system has a definite tie-in with the amount of oil
found in the compressor and an insufficient charge may
eventually lead to an oil build-up in the evaporator.
COMPRESSOR SERIAL NUMBER
The compressor serial number is located on the serial
number plate on top of the compressor. The serial num­
ber consists of a series of numbers and letters. This
serial number should be referenced on all forms and
correspondence related to the servicing of this part.
PERIODIC SERVICE
charge. The glass should be clear, although during
milder weather it may show traces of bubbles. Foam
in the flow indicates a low charge. No liquid visible
and no temperature differential between compressor
inlet and outlet lines, indicates no charge.
5. Check hose clamp connections. If clamp screw
torque is less than 10 lb. in., retighten to 20-25 lb.
in. Do not tighten to new hose specifications or hose
leakage may occur. Leak test the complete system.
6. If there is evidence of an oil leak, check the com­
pressor to see that the oil charge is satisfactory.
CHEVROLET TRUCK SERVICE MANUAL