PERFORMANCE TESTS - CONTINUED - TM-9-2320-303-24-10131

TM 9-2320-303-24-1

AIR CONDITIONING SYSTEM TROUBLESHOOTING AND TESTING - CONTINUED

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PERFORMANCE TESTS - CONTINUED

(d) A quick test to check that poor system performance is caused by the condenser is to direct a spray of

water onto the condenser while the system is running. If the air conditioner cools better because of the

assist provided by the water, it is a sign that the condenser is not working.

(e) When troubleshooting a suspected condenser problem, remember that the problem may be caused by

the radiator transferring high levels of heat to the condenser.

(5)

Thermostatic Switch:

(a) IMPORTANT: Before troubleshooting the thermo-static switch, notify your supervisor to check for a

full charge of refrigerant in the system. The compressor will not operate, or will cycle too often, if

there is not enough refrigerant in the system.

(b) Quick or delayed cycling of the compressor may be caused by a thermostatic switch that is working,

but is out of adjustment. If, after doing the tests below, the switch seems to be out of adjustment,

replace it (the thermostatic switch cannot be recalibrated).

Be sure the compressor clutch is operating correctly.

Expose the evaporator coil.

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

Place an accurate thermometer in contact with a tube on the evaporator coil. Be sure 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).

If the compressor did not engage when the temperature was above the accepted high range, do the following test:

(1)

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.

(2)

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 disen-

gaged.

(a) 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.

(b) 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.

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

batteries.

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 build-up mean a blockage. Parts that often freeze up are probably corroded or inoper-

ative 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,

notify your supervisor.

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