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| Illustration 1 | g01068571 |
The main power relay distributes power to the brake fuse and to the backup alarm fuse through 112-PU wires. Power transfers across the brake fuse into the 110-GN wire. The 110-GN wire delivers power to contacts 1 and 3 of the parking brake switch, to contact 6 of the propulsion lever, and to the contact 3 of the neutral switch relay. The backup alarm fuse distributed power to contact 5 of the reverse switch.
With the parking brake switch ON, contact 3 and contact 4 are closed, and power is delivered to 419-YL wire. The 419-YL delivers power to the parking brake indicator, the coil and contact 5 of the number two brake relay, and to the coil of the number one brake relay. The parking brake indicator illuminates, and the coils of the relays energize.
When the number one brake relay is energized, the brake solenoid is de-energized, and the parking brake is engaged. Regardless of the position of the propulsion lever, the parking brake remains engaged when the parking brake switch is ON.
Even with the propulsion lever out of the NEUTRAL position, the parking brake will remain engaged if the parking brake switch is moved from the ON position to the OFF position. When the propulsion lever is out of NEUTRAL, the neutral switch is open, and the coil of the neutral switch relay is de-energized. Power transfers from the 110-GN wire into the C720-BU wire, and across contact 3 and contact 4 of the neutral switch relay. The C720-BU wire transfers power to contact 3 of the number two brake relay.
When the parking brake switch is moved from the ON to the OFF position, contacts 3 and 4 of the switch open. Power can no longer travel across the contacts and into the 419-YL wire. Ordinarily, this would cause the coil in the number one and the coil in the number two brake relays to de-energize. When the coils are de-energized, the parking brake will release. However, since voltage is available at contact 3 of the number two brake relay, power immediately transfers into the 419-YLwire, and the coils of the number one and the number two brake relays remain energized. The parking brake indicator will remain illuminated, and the parking brake will remain engaged until the propulsion lever is moved back to NEUTRAL.
The parking brake will release when the parking brake switch is moved from the ON to the OFF position and while the propulsion lever is in the NEUTRAL position. With the parking brake switch in the OFF position, contact 1 and contact 2 are closed. Power transfers through the F765-BR wire to contact 3 of the number one brake relay. Contacts 3 and 4 of the number one brake relay are closed. Power transfers to the coil of the neutral brake solenoid. The neutral brake solenoid is energized, and the parking brake is released. However, since the propulsion lever is in NEUTRAL, the machine will not move.
When the propel lever is in REVERSE, the reverse switch is closed. Under this condition, the power transfers to the backup alarm, and the alarm sounds.