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 monitoring air pressure for safe operation of all air-operated compo-
nents of the vehicle.
The dual air brake system consists of two independent air brake systems that use a single set of brake controls. Each sys-
tem 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 inoperative. Front brakes will con-
tinue to be operated by secondary system air pressure. In addition, trailer brakes will be operated by the secondary sys-
tem. Loss of secondary system air pressure causes the front axle brakes to become inoperative. Rear service brakes and
trailer brakes will be operated by the primary system.