AIR CONDITIONING SYSTEM TESTS, INSPECTIONS, AND ADJUSTMENTS - CONTINUED
REFRIGERANT COMPRESSOR TEST - CONTINUED
WARN I N G
· Accidental machine starting can cause injury or death to personnel working on machine.
· To avoid accidental machine starting, turn battery disconnect switch to OFF position and remove key. If
machine is not equipped with a battery disconnect switch, disconnect battery cables from battery and tape
· Place a DO NOT OPERATE tag at battery disconnect switch location to inform personnel that machine is
being worked on.
N OT E
Electrical power supply to compressor should be switched OFF in order to perform this test.
Test Rotation. Rotate compressor in direction of belt travel by turning nut on end of main shaft of compressor. Rotation
should be smooth with no binding. If not, replace compressor (WP 0192 00).
Check Charge Level. AC system must be correctly charged per Caterpillar specification or an incorrect diagnosis will
occur. Recovering, evacuating, and recharging with clean refrigerant to correct level is best method of achieving correct
refrigerant charge for system. Charging AC system must be conducted by weighing refrigerant with a calibrated scale in
order to ensure accuracy. Also, be sure to replace oil which was removed during refrigerant recovery with new oil (WP
Test For Low Pressure. Test for low pressure should be performed with ambient temperatures of less than 86°F (30°C).
Park machine in an area not in direct sunlight. Close all cab doors and windows. Block flow of fresh air into cab. If AC
system is equipped, bypass low pressure switch. Start machine. Operate machine at high idle. Turn ON AC (TM 5-3805-
290-10). Set cab blower on LOW. After 10 to 15 minutes of operation, measure low-side pressure at refrigerant com-
pressor. If pressure reading is less than 10 psi (69 kPa) then suction valves of compressor are operating correctly (WP
0191 00). If not, replace compressor (WP 0192 00).
N OT E
If cab temperature is above 77°F (25°C), then cab blower may need to be set to HIGH in order to reduce
temperature before starting procedure.
Test For High Pressure. Start engine and set speed at approximately 1,200 rpm. Turn ON AC. Place a sheet of card-
board over condenser in order to block flow of air. Limiting flow of air over condenser will cause discharge pressure of
compressor to increase. Check if discharge of compressor is able to increase up to 350 psi (2,414 kPa). Once specified
pressure is reached, immediately remove cardboard. If compressor passes test, discharge valves are operating correctly
(WP 0191 00). If not, replace compressor (WP 0192 00).
END OF WORK PACKAGE
0018 00-17/(0018 00-18 Blank)