Chevrolet 1980 Light Duty Truck Service Manual page 58

1B-12 AIR CO N D ITIO N IN G
CAUTION: Do not use lighted detector in
any place w here combustible or explosive
gases, dusts or vapors may be present.
Operating Detector
1. Determine if there is sufficient refrigerant in the
system for leak testing.
2. Open control valve only until a low hiss of gas is
heard, then light gas at opening in chimney.
3. Adjust flame until desired volume is obtained. This
is most satisfactory when blue flame is approximately 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.
Since R-12 is heavier than air, it is good practice to
place open end of sampling tube immediately below point
being tested, particularly in cases of small leaks.
CAUTION: Do not breathe the fumes th at
are produced by the burning of R-12 gas
in the detector flam e, since such fumes
can be toxic in large concentrations.
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 leaks, the flame will clear to an almost colorless
pale-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.
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 particularly to the front seal.
PRESSURE CYCLING CCOT SYSTEM - C60, CK
and G MODELS,
Compressor clutch cycling on CK&G Series C60
CCOT AC Systems is accomplished through the use of a
pressure sensing switch, (See Figure IB-21 &1B-22) located
near the top of the accumulator. The switch performs two
functions in the system. In addition to cycling the
compressor on and off to control refrigerant flow, the switch
shuts off the compressor clutch when pressure falls to a
predetermined level, indicating low refrigerant charge in the
system.
When diagnosis (See Chart IB-3 and IB-4) indicates
replacement of the switch is necessary, it should be noted
that it will not normally be necessary to discharge the A/C
system, as the pressure switch fitting on the accumulator
is equipped with a schrader type valve.
When replacing the pressure cycling switch, a new
oiled "O" ring must be installed and the switch must be
torqued to 10 N-m (7.5 ft. lb.). Do not exceed this torque
as the threads in the accumulator may be stripped.
LIG H T T R U C K S ER V IC E M AN UAL