AIR CONDITIONING SYSTEM TROUBLESHOOTING AND TESTING - CONTINUED
PERFORMANCE TESTS - CONTINUED
(a) Connect a voltmeter or a test light from one of the terminals on the thermostatic switch to ground.
Repeat this test with the other terminal on the switch.
With the engine running and the air conditioner and blower on, both terminals will show voltage when
the compressor should be engaged; one terminal will show voltage when the compressor should be
If there is no voltage, there is a problem in the electrical system from the batteries to the thermostatic
switch. Check all circuits for the cause, and repair or replace the wiring or parts.
In all other cases where the compressor is not engaging and disengaging properly, the thermostatic
switch is the cause. Replace it with a new switch (TM 9-2320-302-20).
Shut down the engine and, to prevent accidental electric shock or shorting during dash assembling, discon-
nect the batteries.
Assemble the dash.
A restricted suction line causes low suction pressure at the compressor and little or no cooling. A restriction in a
line between the compressor and the expansion valve can cause high discharge and low suction pressure, and
Usually, areas of ice or frost buildup mean a blockage. Parts that often freeze up are probably corroded or inopera-
tive and should be replaced. Parts (such as the expansion valve) that freeze up once in a while may do so because
of moisture in the system, which will cause the moisture indicators element to turn white or pink; if this happens,
recover the refrigerant charge, evacuate/recycle the system refrigerant, replace the receiver-drier, and install a new
charge (WP 0112 00).
Whenever repairs are made to any air conditioner parts that hold refrigerant, you must discharge, purge or flush (if con-
taminated), evacuate, charge, and leak test the system. In a good system, refrigerant lines are always under pressure and
you should disconnect them only after the air conditioning system has been discharged to a refrigerant recovery unit
through the service valves on the compressor (WP 0112 00).
Use care to prevent refrigerant from touching your skin or eyes. Liquid refrigerant, when exposed to the air,
quickly evaporates and will freeze skin or eye tissue. Serious injury or blindness may result if you come in
contact with liquid refrigerant.
Refrigerants are safe when used under the right conditions. Always wear safety goggles and non-leather gloves while
discharging, purging, flushing, evacuating, charging, and leak testing the system. Do not wear leather gloves; when
refrigerant gas or liquid contacts leather, the leather will stick to your skin.
Refrigerant splashed in the eyes should first be treated with a few drops of sterile mineral oil in the eyes, then rinsed
with a weak boric acid solution. Do not rub the eyes. Call a doctor right away.
Refrigerant splashed on the skin should be treated the same as for frostbite: gently pour cool water on the area, but do
not rub the skin. Keep the skin warm with layers of soft, sterile cloth. Call a doctor right away.