THEORY OF OPERATION - CONTINUED
The air system consists of the air compressor, air dryer, air reservoirs, and various air lines.
Also included in the air system are air pressure gages, located on the instrument panel, for mon-
itoring air pressure for safe operation of all air-operated components of the vehicle.
The dual air brake system consists of two independent air brake 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 and the secondary system
operates the service brakes on the front axle. On tractor-trailer configurations, service
brake signals from both systems are sent to the trailer.
Loss of air pressure in the primary system causes the rear service brakes to become inop-
erative. Front brakes will continue to be operated by secondary system air pressure. In
addition, trailer brakes will be operated by the secondary system. Loss of secondary sys-
tem air pressure causes the front axle brakes to become inoperative. Rear service brakes
and trailer brakes will be operated by the primary system.