PERFORMANCE TESTS - CONTINUED - TM-9-2320-303-24-20035

TM 9-2320-303-24-2

AIR CONDITIONING SYSTEM TROUBLESHOOTING AND TESTING - CONTINUED

0227 00

PERFORMANCE TESTS - CONTINUED

(1)

Ensure the compressor clutch is operating correctly.

(2)

Expose the evaporator coil.

(3)

Start the engine. Place the air conditioner control at its coldest setting; turn on the air conditioner and the

fan.

(4)

Place an accurate thermometer in contact with a tube on the evaporator coil. Ensure the thermometer is in

good contact with the tube or you will get a wrong reading.

When the temperature drops below 31F to 36F (-1C to 2C), the compressor clutch should disengage

and remain this way until the temperature rises to 39F to 44F (4C to 7C).

(5)

If the compressor did not engage when the temperature was above the accepted high range, do the follow-

ing test:

(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.

(b) 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

disengaged.

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 (WP 0214 00).

(6)

Shut down the engine and, to prevent accidental electric shock or shorting during dash assembling, discon-

nect the batteries.

(7)

Assemble the dash.

Line Restrictions.

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

insufficient cooling.

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 indicator's element to turn white or pink; if this happens,

recover the refrigerant charge, evacuate/recycle the system refrigerant, replace the receiver-dryer, and install a new

SAFETY PRECAUTIONS

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 0297 00).

0227 00-3