General Information
A dual air brake system consists of two independent air systems that use a single set of brake controls. Each system has its own reservoirs, plumbing, and brake chambers. The primary system operates the service brakes on the rear axle; the secondary system operates the service brakes on the front axle. Service brake signals from both systems are sent to the trailer.
Warning: Do not operate the vehicle with the front brakes backed off or disconnected. Backing off or disconnecting the front brakes will not improve vehicle handling and may lead to loss of vehicle control, resulting in property damage or personal injury.
The psi of both the primary and secondary system appear on the brake air gauge on the driver display, shown in Fig. .
Fig. 1, Brake Air Gauge on Driver Display
If air pressure drops below approximately 70 psi (483 kPa) in either system, a warning telltale illuminates. See Fig. . If the park brake is not set, an audible alert also activates.
Fig. 2, Low Brake Air Pressure Telltale
If the low air pressure warning displays, check the air 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 rear service brakes will not be operating at full capacity, causing a longer stopping distance. Bring the vehicle to a safe stop and have the air system repaired before continuing.
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.
Before a vehicle with insufficient brake system air pressure can be moved, the spring parking brakes must be released by applying an external air source at the gladhands, or by manually caging the parking brake springs.
Warning: Do not cage the spring parking brakes and then drive the vehicle. If you do this, there is no way to hold the vehicle stationary after coming to a complete stop and releasing the service brake pedal. This could result in serious personal injury or vehicle damage. Before releasing the spring parking brakes, make the connection to a towing vehicle or chock the tires.
After correcting the brake system problem, uncage the spring parking brakes before resuming normal vehicle operation.
Primary Air Brake System
Loss of air pressure in the primary air system causes the rear service brakes to become inoperative. The secondary air system continues to operate the front brakes and, if equipped, the trailer brakes.
Secondary Air System
Loss of air pressure in the secondary air system causes the front axle brakes to become inoperative. The primary air system continues to operate the rear service brakes and, if equipped, the trailer brakes.
eCompressor
The eCascadia is equipped with an electric air compressor (eCompressor). Prior to normal operation, the eCompressor needs to warm up to operating temperature. Warm-up may take up to 5 minutes depending on the outside air temperature. The eCompressor runs continuously during this time. This is followed by a brief period during which the electric air dryer purges contaminants out of the system, and the eCompressor cycles on, then off. Cycling may occur several times if vehicle was improperly shutdown. During normal operation, the eCompressor only runs when the air tanks are at low pressure.