GLASS 9R4027 - Caterpillar

Illustration 1 g02698856
Location of parking brake control valve
Illustration 2 g02253993
Parking brake control valve (Top view)The operators platform is removed for clarity.The parking brake control valve is located on the right side of the machine above the service center.
Illustration 3 g02702516
Location of parking brake switch on the right side control panel
Illustration 4 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 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 ECM machine startup
The parking brake switch transitions from applied to released and either the left-hand armrest is down with operator not present or steering is enabled.When the parking brake is released, solenoid valve (2) is energized. Pressure oil (A) from the rear 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 applied position.
The ECM is powered down.
The engine is going through normal startup sequence.If the parking brake is applied, the parking brake will be locked applied if all of the conditions listed below are met.
The actual gear is Neutral
Ground speed is zero
Left-hand armrest is stowed or both the left-hand armrest is down and a steering not aligned event has occurred.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 5 g02413496
Monitoring system display (4) Parking brake indicator light (5) Action lightWhen 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 (4), a flashing action light (5) 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.