PLATE 1408448 - Caterpillar

Illustration 1 g06268596
Parking Brake Control Valve
Illustration 2 g06268541
Parking brake switch
The parking brake control valve (1) is mounted on the upper hitch plate under the cab.
Illustration 3 g02413477
Schematic of parking brake control valve (energized)
(1) Pressure sensor
(2) Solenoid valve
(3) Valve
(A) Pressure oil
(B) Tank oil
(C) To parking brake actuatorThe parking brake control valve controls the flow of pressure oil for the parking brake actuator. The parking brake will be released if the conditions listed below are met.
The operator is present and the parking brake switch transitions from the Engaged position to Released position.
The parking brake switch is in the release position and the ground speed is greater than 2 km/h (1.2 mph) for 200 milliseconds at Power Train ECM startupWhen the parking brake is released, solenoid valve (2) is energized. Pressure oil (A) from the front service brake accumulator flows through solenoid valve (2) to the end of valve (3). Valve (3) shifts to allow pressure oil to flow to parking brake actuator (C). The pressure of the oil compresses the spring in the parking brake actuator. The parking brake disengages. The pressure of the oil keeps the parking brake in the DISENGAGED position.The parking brake will be applied if any of the conditions listed below are met.
The parking brake switch is in the Engaged position.
The Power Train ECM is powered down.
The engine is going through normal startup sequence.If the parking brake is engaged, the parking brake will be locked if all of the conditions listed below are met.
The actual gear is Neutral
Ground speed is zero
Left-hand armrest is in Raised position, or the left-hand armrest is in Lowered position and the left-hand steering control is not aligned with the machine.When the parking brake is applied, solenoid valve (2) is deenergized. The flow of oil from the brake accumulator is blocked. Oil in the parking brake actuator flows back to the hydraulic tank. The force of the spring in the parking brake actuator is greater than the pressure of the oil. The spring will engage the parking brake.
Illustration 4 g06270215
Advisory indicator for the parking brake and the Action light.
When the oil pressure for the parking brake actuator decreases below 6890 kPa (1000 psi), the Caterpillar Monitoring System initiates a Warning Category 3 alarm. The indications of a Warning Category 3 include the following items: the parking brake indicator light, a flashing action light on the monitoring system display and the action alarm.The transmission returns to the NEUTRAL position if the transmission is in either first speed forward or first speed reverse. This shifting will occur when the parking brake engages.Note: The parking brake can be manually engaged and disengaged when the pressure in the system is above 10300 kPa (1495 psi). However, if the system pressure is below 10300 kPa (1495 psi), actuation force increases.