Chevrolet 10 Series 1968, Service Manual

Page: 47 / 713

HEATER AND AIR CONDITIONING 1A-16
The vacuum pump (fig. 28) is a component part of
Charging Station J-8393, described previously. The fo l­
lowing precautions should be observed relative to the
operation and maintenance of this pump.
• Make sure dust cap on discharge outlet of vacuum
pump is removed before operating.
® Keep all openings capped when not in use to avoid
moisture being drawn into the system,
e Oil should be changed after every 250 hours of
normal operation.
To change oil, simply unscrew hex nut located on back
side of pump, tilt backward and drain out oil (fig. 28).
Recharge with 8 ounces of vacuum pump oil Frigidaire
150 or equivalent (fig. 28). If you desire to flush out the
pump, use this same type clean oil. Do not use solvent.
NOTE:
Improper lubrication will shorten the
life of pump.
• If this pump is subjected to extreme or prolonged
cold, allow it to remain indoors until oil has reached
approximate room temperature. Failure to warm
oil will result in a blown fuse.
• A five ampere time delay cartridge fuse has been
installed in the common line to protect the windings
of the compressor. The fuse will blow if an ex­
cessive load is placed on the pump. In the event the
fuse is blown, replace with a five ampere time delay
fuse - do not use a substitute fuse as it will result in
damage to the starting windings.
• If the pump is being utilized to evacuate a burnt-out
system, a filter must be connected to the intake
fitting to prevent any sludge from contaminating the
working parts, which will result in malfunction of the
pump.
• Do not use the vacuum pump as an air compressor.
LEAK TESTING THE SYSTEM
Whenever a refrigerant leak is suspected in the system
or a service operation performed which results in dis­
turbing lines or connections, it is advisable to test for
leaks. 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. It is better to test and be sure, if in doubt,
than to risk the possibility of having to do the job over
again.
NOTE:
The use of a leak detecting dye within
the system is not recommended because of the
following reasons:
1. Refrigerant leakage can exist without any oil leakage.
In this case the dye will not indicate the leak, how­
ever, a torch detector will.
2. The addition of additives, other than inhibitors, may
alter the stability of the refrigeration system and
cause malfunctions.
3. Dye type leak detectors which are insoluble form a
curdle which can block the inlet screen of the ex­
pansion valve.
Leak Detector
Tool J-6084 (fig. 29) 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.
CA U TIO N : Do not use lighted detector in any
place where combustible or explosive gases,
dusts or vapors may be present.
Fig . 28—Vacuum Pump
O perating 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.
C O R D TO PUMP PUMP D IS C H A R G E
110 A C S O U R C E INLET OUTLET
FIVE AMP
TIME D ELA Y
FUSE
CHEVROLET TRUCK SERVICE MANUAL