The air system provides the air supply to operate the service brakes, the parking brake, the engine throttle, the
transmission range shift and rear axle disconnect.
The air system is pressurized by an engine-mounted air compressor and this pressure is stored in three air reservoirs
installed underneath the frame to the rear of the front axle. From these reservoirs, air is provided for operation of the
above mentioned components.
An air pressure gauge is provided in the cab on the front console. The green arrow indicates primary air pressure, while
the red arrow indicates secondary pressure.
Air Compressor and Air Governor
The compressor, mounted on and driven by the engine, is regulated by an air governor which vents the compressor when
a pressure of 120 psi (827.4 kPa/8.27 bar) is sensed in the air system. When pressure drops to 100 psi (689.5 kPa/6.895
bar), the governor will allow the compressor to supply the air system to maintain proper system pressure.
Through reciprocating motion, the piston in the compressor compresses air with every cycle.
The air dryer removes moisture from the air system by using a desiccant cartridge. Water is drained from the air dryer via
the automatic drain valve.
Compressed air passes through the air dryer to the supply reservoir. The supply reservoir helps cool heated air and
contains an automatic drain valve to vent off condensed water from the cooling air. A 150 psi (1034.25 kPa/10.34 bar)
safety valve is installed on the supply reservoir for excess pressure protection (from the supply reservoir, pressurized air
flows to the primary and secondary reservoirs).