GEAR 1405569 - Caterpillar

Accessory Hydraulic System Control
Input Signals
Illustration 5 g06259858
Accessory Control System Diagram
(1) Operator display
(2) Transmission ECM
(3) Tow mode auxiliary relay
(4) Tow mode auxiliary solenoid
(5) Hood switch
(6) Canopy switch
(7) Machine ECM
(8) Steering ECM
(9) I/O module
(10) Hood raise solenoid
(11) Hood lower solenoid
(12) Electric pump relay"K51"
(13) Auxiliary power unit motor
(14) Canopy lower solenoid
(15) Canopy raise solenoid
(16) Output signal
(17) CAN signalNote: The above illustration shows the general layout of the accessory control system. Refer to the machine electrical schematic for detailed wiring information.Under normal operation, the accessory control system does not contain input signals. Hood switch (5) and canopy switch (6) receive unswitched power from fuse"F28" on the power distribution board.When the engine is not operational, tow mode may be enabled. In this case, transmission ECM (2) receives a tow mode input signal from operator display (1) through CAN line (17). This signal changes the"Tow Mode Status". The status value is"Enabled" or"Disabled."When the"Tow Mode Status" value is"Enabled," the auxiliary hydraulic system input signals are functional from the various operator control stations. In this case, each auxiliary hydraulic system command is read by module (9).Output Signals
Hood switch (5) generates output signals (16) to control the hood. When the switch is in the RAISE position, an output signal is sent to hood raise solenoid (10) and auxiliary power unit motor relay (12). When the switch is in the LOWER position, an output signal is sent to hood lower solenoid (11) and auxiliary power unit motor relay. In either case, the APU motor relay energizes auxiliary power unit motor (13) to drive the APU pump.Canopy switch (6) generates output signals (16) to control the canopy. When the switch is in the RAISE position, an output signal is sent to canopy raise solenoid (15) and auxiliary power unit motor relay (12). When the switch is in the LOWER position, an output signal is sent to canopy lower solenoid (14) and auxiliary power unit motor relay. In either case, the APU motor relay energizes auxiliary power unit motor (13) to drive the APU pump.Tow Mode
When the tow mode is enabled, transmission ECM (2) generates an output signal to the tow mode auxiliary relay"K32" (3). In this case, the relay energizes tow mode auxiliary solenoid (4). This action directs auxiliary power unit pump oil to the main auxiliary hydraulic system.When a main auxiliary hydraulic system command is generated, I/O module (9) on the power distribution board reads the command. The I/O module then generates an output signal to the electric pump relay"K51" (12). During the command, the electric pump relay energizes auxiliary power unit motor (13) to drive the APU pump.Operating Logic
The accessory hydraulic system requires auxiliary power unit motor (13) to be energized to operate. When the electric pump relay"K51" (12) is energized, the APU motor is energized and the APU pump is actuated. In this case, the accessory hydraulic system is pressurized.When hood raise solenoid (10) is energized, system supply oil is directed to raise the hood. When hood lower solenoid (11) is energized, system supply oil is directed