SAFETY PRECAUTIONS - CONTINUED - TM-9-2320-312-24-10802

TM 9-2320-312-24-1

AIR CONDITIONING SYSTEM GENERAL MAINTENANCE AND TESTING - CONTINUED

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SAFETY PRECAUTIONS - CONTINUED

Changes in both federal and state laws will affect the way dealerships service air conditioning systems. Under current

federal laws, refrigerant must be recovered and recycled by all users to protect environment, and not released into atmo-

sphere. Many service operations not directly involving the air conditioning system require release of refrigerant charge.

Under new regulations, dealerships not having required recovery and recycling equipment (and properly trained and cer-

tified personnel) will not be allowed to do any of this service work.

Because of its very low boiling point, refrigerant must be stored under pressure. To prevent refrigerant cans from

exploding, never expose to temperatures higher than 125F (52C). Never leave refrigerant cans in the sun, and DO

NOT store them in sun-exposed areas where heat can build up.

PERFORMANCE TESTS

Following is a brief description of symptoms or conditions that could exist if something goes wrong with a refrigerant

part.

Receiver-Drier.

The receiver-drier is normally at outside temperature. To the touch, entire length of unit should be same tempera-

ture. If noticeable cool spots exist, notify your supervisor.

A blockage at receiver-drier inlet will cause high head pressures. Blockages at receiver-drier outlet will cause low

head pressures and little or no cooling.

If moisture indicator color is pink or white (showing system is wet), receiver-drier is saturated with moisture and

must be replaced. Notify your supervisor.

Cooling System.

Although not physically connected, a close tie exists between vehicle air conditioner and cooling system. Poor air

conditioner cooling can be the result of a problem in the cooling system.

If cooling system does not work correctly, heat of engine will rise to abnormal levels. The added heat will transfer

to the air conditioner, other underhood parts, and may make its way into the cab. The added heat makes it neces-

sary for air conditioner to work harder and, at the same time, reduces air conditioner ability to cool down air in cab.

Also, if water regulating valve is not closing fully, heat will enter cab, giving the impression that the air condition-

ing system is not working.

Expansion Valve.

Problems that start in expansion valve show up as follows:

(1)

When expansion valve is stuck closed, evaporator coil and expansion valve will be at outside temperature.

(2)

When expansion valve is stuck open, both coil and valve will be extremely cold with frost or ice buildup.

Because expansion valve channels are very small, blockages in system tend to be found here (valve is very sensi-

tive to contamination). Usually, contaminant is water. Less than a drop of water is all it takes to make valve inoper-

ative. When water reaches valve, extreme cold that results from pressure drop freezes water, forming a block of ice

in valve. After system shuts down and valve warms up, the ice melts and valve operates again, only to freeze up

when moisture returns.

On-and-off operation of expansion valve means that receiver-drier is not removing moisture from system. These

contaminants should cause moisture indicator element to turn white and then pink.

AC Compressor.

Compressor problems usually show in one of four ways: abnormal noise; seizure; leakage; or low suction and dis-

charge pressures.

Resonant compressor noises are not causes for alarm. Irregular noise or rattles are likely to be caused by broken

parts.

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