AD22 Underground Articulated Truck Braking System Caterpillar

The Machine Electronic Control Module ECM receives an input signal from the hydraulic accumulator oil pressure sensor on the control valve. If a braking system failure occurs and the accumulator oil pressure is lost, the Machine ECM will engage the parking brake.

Brake Accumulator Oil Pressure Sensor

Alert Indicator

Illustration 1	g06239665
(1) Brake accumulator oil pressure sensor

Brake accumulator oil pressure sensor (1) is on the main control valve. The brake valve is on the left side of the front frame, in the transmission compartment.

The pressure of the brake accumulator oil corresponds to the voltage signal of the sensor. The changes in the voltage represent changes in the brake accumulator oil pressure. The voltage signal is an input of the Machine Electronic Control Module (Machine ECM).

For the brake accumulator oil pressure sensor the low accumulator pressure warning light will activate at 11730 ± 345 kPa (1700 ± 50 psi).

When the engine is started, brake accumulator oil pressure increases. The Machine ECM receives a signal from brake accumulator oil pressure sensor. (1). The Machine ECM then sends a signal to the Monitoring System over the CAN Data Link. The Monitoring System will then turn off the brake accumulator oil pressure alert indicator on the Monitoring System display.

If the brake accumulator oil pressure decreases, a signal is sent from oil pressure sensor (1) to the Machine ECM. The Machine ECM then sends a signal to the Monitoring System over the CAN Data Link. The Monitoring System will then turn on the brake accumulator oil pressure alert indicator on the Monitoring System display. The brake accumulator oil pressure alert indicator will warn the operator of low brake accumulator oil pressure.

Brake Application

Illustration 2	g06239665
(1) Brake accumulator oil pressure sensor

Brake accumulator oil pressure sensor (1) is on the main control valve. The valve is on left side of the front frame, in the transmission compartment.

The pressure of the brake accumulator oil corresponds to the voltage signal of the sensor. The changes in the voltage represent changes in the brake accumulator oil pressure. The voltage signal is an input of the Electronic Control Module (Machine ECM).

The deactivation pressure for the brake accumulator oil pressure sensor, brake application, is 8274 ± 345 kPa (1200 ± 50 psi).

When the engine is started, brake accumulator oil pressure increases. The Machine ECM receives this signal and will allow the parking brake to be disengaged.

If the brake accumulator oil pressure decreases, a signal is sent from oil pressure sensor (1) to the Machine ECM. The Machine ECM then sends a signal to the Monitoring System over the CAN Data Link. The Monitoring System will then turn on the brake accumulator oil pressure alert indicator on the Monitoring System display. The brake accumulator oil pressure alert indicator will warn the operator of low brake accumulator oil pressure. If machine operation is continued and the brake accumulator hydraulic oil pressure further decreases, the Machine ECM will engage the parking brake.

The parking brake will remain engaged until the brake accumulator oil pressure increases. The operator must then cycle the parking brake switch from the ON position to the OFF position to disengage the parking brake.

Note: The park brake switch must be cycled before the park brakes will release.