Chevrolet Light Duty Truck 1973 Service Manual page 69

Common sense should be the governing factor in
performing any leak test, since the necessity and extent
of any such test will, in general, depend upon the nature
of the complaint and the type of service performed on
the system.
Leak Detector
Tool J-6084 (fig. 48) is a propane gas-burning torch
which is used to locate a leak in any part of the system.
Refrigerant gas drawn into the sampling tube attached
to the torch will cause the torch flame to change color in
proportion to the size of the leak. Propane gas fuel
cylinders used with the torch are readily available
commercially throughout the country.
Do not use lighted detector in
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any place where 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 approx­
imately 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
Fig. 48-Leak Detector
HEATER A N D AIR C O N D IT IO N IN G
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,
particularly in cases of small leaks.
Do not breathe the fumes that
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are produced by the burning of R-12 gas in
the detector flame, 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.
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 equal­
ize). 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.
AVAILABILITY OF REFRIGERANT-12
Refrigerant-12 is available in 30 lb. and in 15 oz.
disposable containers.
Normally, air conditioning systems are charged making
use of the J-8393 Charging Station which uses the 30 lb.
container. Evacuating and charging procedures are noted
later in this section.
The 15 oz. disposable cans are generally used for
miscellaneous operations such as flushing.
The following precautions should
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be observed when adding refrigerant to a
system using 15 oz. disposable cans:
1. Do not charge while compressor system is hot.
2. Empty container completely before disposing.
3. Use opening valves designed for use with container
- follow valve m anufacturer's directions carefully.
4. Always use pressure gauges before and during
charging.
5. NEVER connect on high pressure side of system or
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LIGHT DUTY TRUCK SERVICE MANUAL