RAIL 4V2677 - Caterpillar

Illustration 1 g03385290
Heating air conditioning circuit
The components of the heating and air conditioning circuit are the:
Fan speed switch
Air conditioning thermostat switch
Fan motor
Pressurizer fan motor
Refrigerant pressure switch
Compressor clutch solenoid
Illustration 2 g03392290
(1) Fan speed switch
(2) Heater thermostat switch
(3) Air conditioning thermostat switch
Illustration 3 g03392291
Internal components of the air conditioning unit
(1) Fan speed switch
(3) Temperature control
(4) Fan motor
Illustration 4 g00987473
Side view of cab
(5) Pressurizer fan motor
Illustration 5 g00987474
Right side view of engine
(6) Refrigerant pressure switch
(7) Compressor clutch solenoidWith the key start switch in the ON position, 24 V power is supplied via circuit breaker #6 to fan speed switch (1).Fan speed switch (1) is a four position switch which controls operation of fan motor (4) and pressurizer fan motor (5). When fan speed switch (1) is turned to LOW, MEDIUM, or HIGH position, 24 V power is supplied to air conditioning thermostat switch (3), fan motor (4) and pressurizer fan motor (5). Air conditioning thermostat switch (3) controls the required level of cooling and protects the system from over-cooling. Pressurizer fan motor (5) and fan motor (4) will be on.When air conditioning thermostat switch (3) contacts are closed, 24 V power is supplied to refrigerant pressure switch (6). When the air conditioning system is charged with refrigerant, refrigerant pressure switch (6) is closed. 24 V power is then supplied to energize compressor clutch solenoid (7). Energizing compressor clutch solenoid (7) activates the compressor causing the refrigerant pressure to rise.When the refrigerant pressure increases higher than the set value of refrigerant pressure switch (6), the switch opens. The open switch interrupts the power supply to compressor clutch solenoid (7). The compressor is now deactivated and refrigerant pressure will slowly decrease.When the refrigerant pressure decreases to the normal set value of refrigerant pressure switch (6), the switch will close and the compressor will be activated.If the refrigerant pressure decreases below the normal operating pressure, refrigerant pressure switch (6) will be open. Opening the switch will interrupt the power supply to compressor clutch solenoid (7) and the compressor will not operate. The system will not activate until the system has been serviced.