HUB 8P0768 - Caterpillar

Alert Indicator
Illustration 1 g01139600
(1) Brake accumulator oil pressure switch for the alert indicator The brake accumulator oil pressure switch for the alert indicator is located on the left side of the rear frame, under the brake accumulator.The brake accumulator oil pressure switch for the alert indicator senses oil pressure in the brake accumulator circuit.When the engine is started, brake accumulator oil pressure increases.When the oil pressure increases to the actuation pressure for pressure switch (1), the pressure switch will close. The Caterpillar Monitoring System receives a signal from the oil pressure switch. The Caterpillar Monitoring System will then turn off the brake accumulator oil pressure alert indicator on the Caterpillar Monitoring System display.If the brake accumulator oil pressure decreases to the deactuation pressure for pressure switch (1), the switch will open and the brake accumulator oil pressure alert indicator on the Caterpillar Monitoring System display will come on. This will warn the operator of low brake accumulator oil pressure.Reference: For information on the brake accumulator oil pressure switch for the alert indicator, refer to Systems Operation, Testing and Adjusting, Machine Electrical System, "Alert Indicator - Brake Accumulator Oil Pressure".Brake Application
Illustration 2 g01139601
(2) Brake accumulator oil pressure switch for brake application The brake accumulator oil pressure switch for brake application is located on the left side of the rear frame, under the brake accumulator.The brake accumulator oil pressure switch for brake application senses oil pressure in the brake accumulator circuit. The brake accumulator oil pressure switch for brake application is an input of the Power Train ECM.When the engine is started, brake accumulator oil pressure increases. When the oil pressure reaches the actuation pressure for pressure switch (2), the switch will close. The Power Train ECM receives this signal and will allow the parking brake to be disengaged.If the brake accumulator oil pressure decreases to the deactuation pressure for pressure switch (1), the switch will open and the brake accumulator oil pressure alert indicator on the Caterpillar Monitoring System display will come on. This will warn the operator of low brake accumulator oil pressure. If machine operation is continued and the brake accumulator hydraulic oil pressure decreases to deactuation pressure for pressure switch (2), the switch will open. Pressure switch (2) sends a signal to the Power Train ECM. The Power Train ECM will engage the parking brake.The parking brake will remain engaged until the brake accumulator oil pressure increases above the actuation pressure for pressure switch (2). The operator must then cycle the parking brake switch from the ON position to the OFF position in order to disengage the parking brake.Reference: For information on the brake accumulator oil pressure switch for brake application, refer to Systems Operation, Troubleshooting, Testing and Adjusting, Power Train Electronic Control System, "Switches".