SHEET AS 3420932 - Caterpillar

Parking Brake Control (Switch) (26) - Move the parking brake switch to the OFF position to release the parking brake. Move parking brake switch (19) to the ON position to engage the parking brake.Parking Brake Reset Valve (27)
Parking Brake Reset Valve (27) - When the air system is drained, the parking brake reset valve will not allow the parking brake to release until you have reset the valve. Press down the button on the parking brake reset valve to reset the valve.The parking brake reset valve is a mechanical valve that will automatically close if the supply pressure from the secondary air reservoir drops below 414 kPa (60 psi). The valve is placed in the air supply line for the parking brake. When this valve actuates, the air supply to the parking brake valve is cut off. This applies the parking brake. Once the parking brake reset valve is applied, the parking brake reset valve will not release until following two events occur:
The air pressure in the secondary air reservoir must be above 414 kPa (60 psi).
The operator must manually reset the valve by pushing in on the popup indicator.The valve will not close during truck operation unless the operator is operating the truck after activation of the low air pressure warning buzzer. The operator will be warned to stop operating the truck because of low air pressure if the pressure drops below 450 kPa (65 psi). If the operator continues to operate the truck, the parking brake reset valve will close when the air pressure drops below 414 kPa (60 psi). This will apply the parking brake.If the system air pressure drops below 414 kPa (60 psi), the amber popup indicator in the cab will rise. The operator cannot push down the popup indicator to deactivate the parking brake until the air system pressure rises above 414 kPa (60 psi). Typically, air pressures that are low enough to automatically activate the parking brake reset valve are experienced only after the machine is shut down and after the system air pressure is purged.As an automatic mechanism, the parking brake reset valve ensures that the parking brake does not release without a specific operator action. The parking brake reset valve will not automatically apply the parking brake when the truck is shut down. The operator must still follow the proper parking and shutdown procedures.Service Brake (28)
Do not use the front wheel brakes for retarding on long steep downgrades.Overheating may occur, causing reduced service life of the brake components.
During normal operation, depress service brake control (pedal) (28) to stop, or slow the machine. The pedal is fully variable. The amount of braking force depends on