950M and 962M Wheel Loaders Power Train, Steering, Braking, Hydraulic, and Machine Systems Caterpillar

Illustration 1	g02413456
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	g03565814
Location of parking brake switch on the right side control panel

Illustration 4	g03565821
Schematic of parking brake control valve (energized) (1) Pressure sensor (2) Solenoid valve (A) Pressure oil (B) Tank oil (C) To parking brake actuator

The 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 startup

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). The oil flows to the parking brake actuator and pressurizes the 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.

• The engine has been commanded to shut off (key off or Engine Idle Shutdown) and ground speed is zero.

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 5	g03565847
Monitoring system display (4) Parking brake indicator light (5) Action light

When the oil pressure for the parking brake actuator decreases below 11370 kPa (1649 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 11700 kPa (1700 psi). However, if the system pressure is below 11700 kPa (1700 psi), actuation force increases.