Operation
Before driving the vehicle, secure all loose items in the cab so that they will not fly forward during a full brake application. Make sure that all occupants are wearing seat belts.
Allow time for the air compressor to build up a minimum of 95 psi (655 kPa) pressure in both the primary and secondary systems. Monitor the air pressure system by observing the dual system air pressure gauges and the low-air-pressure warning light and buzzer. The warning light and buzzer shut off when the pressure in both systems reaches 65 to 73 psi (448 to 503 kPa).
The warning light and buzzer come on if air pressure drops below 65 to 73 psi (448 to 503 kPa) in either system. If this happens, check the air system pressure gauges to determine which system has low air pressure. Although the vehicle's speed can be reduced using the foot brake control pedal, either the front or the rear service brakes will not be operating, causing a longer stopping distance. Bring the vehicle to a safe stop and have the air system repaired before continuing.
During normal braking stops, depress the foot brake control pedal until braking action slows down the vehicle. Increase or decrease the pressure on the pedal so that the vehicle comes to a smooth, safe stop. When the forward speed of the vehicle has decreased to almost the idling speed of the engine, push the clutch pedal in (if equipped) and shift the transmission into Neutral (N). Apply the hand parking brake if the vehicle is to be parked.
Important: In the event of a total loss of service brakes with full system air pressure, use the parking brake control valve (yellow knob) to bring the vehicle to a complete stop in the safest location possible.
The yellow diamond-shaped knob on the control panel actuates the parking brake valve. Pull out the knob to apply the parking brake. See Fig..
Fig. 1, Parking Brake Control Knob
Warning: If the vehicle is equipped with an air suspension system, do not move the vehicle with the air suspension deflated. Doing so could result in a loss of vehicle control, possibly causing personal injury and property damage.
Notice: Do not use the spring brakes if the service brakes are hot, such as after descending a steep grade. Also, do not use the spring parking brakes during freezing temperatures if the service brakes are wet. To do so could damage the brakes if hot, or cause them to freeze during cold weather.
If the brakes are wet, drive the vehicle in Low (L) or First (1) gear and lightly apply the brakes to heat and dry them.
Allow hot brakes to cool before using the parking brake. Always chock the tires.