AD30 Underground Articulated Truck Machine Electrical System Caterpillar

Illustration 1	g01013169
Hoist control circuit

The components of the hoist control circuit are the hoist control position sensor, the body up/tail gate down indicator, the tail gate switch, the hoist retract coil, the hoist eject coil and the Power Train/Chassis Electronic Control Module (Power Train/Chassis ECM).

Illustration 2	g01012919
Cab (1) Hoist control position sensor (behind cover)

Hoist control position sensor (1) is located behind the transmission control console. The hoist control has four positions: RETRACT, HOLD, HOLD and EJECT. The signals from the hoist control position sensor are used by the Power Train/Chassis ECM, which then controls the hoist retract coil and the hoist eject coil. This will eject or retract the dump body.

Illustration 3	g01012916
Dash panel (2) Body up/tail gate down indicator

Illustration 4	g01012923
Rear view of machine (3) Tail gate switch

Illustration 5	g01012914
Right side view of transmission compartment (4) Hoist retract coil (5) Hoist eject coil

Illustration 6	g01012917
Front view of cab (front cover plate removed) (6) Power Train/Chassis ECM

Under certain conditions the Power Train/Chassis ECM neutralizes the transmission. The transmission will only be selectable in FIRST SPEED, SECOND SPEED and THIRD SPEED when the hoist control position sensor is not in the HOLD position, or the tailgate is completely down. The reverse gear neutralizer function is activated when the hoist control position sensor is in the EJECT position.

With the key start switch in the ON position, 24 volt power is supplied from the batteries via circuit breaker #12 to hoist control position sensor (1), body up/tail gate down indicator (2), and Power Train/Chassis ECM (6) .

When the hoist control position sensor is in the RETRACT position, a signal is sent to the Power Train/Chassis ECM. The Power Train/Chassis ECM supplies 1.9 amps of current to hoist retract coil (4) to retract the ejector body.

When the hoist control position sensor is in the EJECT position, the Power Train/Chassis ECM supplies 1.9 amps of current to hoist eject coil (5) to eject the ejector body.

When the hoist control position sensor is in the HOLD position, neither of the hoist coils are receiving current. The directional spool is now in a NEUTRALIZED position. Hydraulic oil can not flow through the hoist control valve.

Note: The hoist control valve will default to the HOLD position if the key start switch is turned to the OFF position or ON position, or if a fault has occurred in the hoist control circuit.

Reference: For more information on the hoist control, refer to Systems Operation, Testing and Adjusting, "Calibration Mode" for the machine that is being serviced.