Section XXII COMPRESSED AIR SYSTEM
The compressed air supply system is the same in all M915 thru M920 vehicles.
2-60. COMPRESSED AIR SYSTEM.
SAFETY VALVE. Vents air when pressure in supply tank rises above 150 psi (1,034 kPa).
TRANSMISSION CONTROL LINE. Air supply to ratio selector valve in cab.
(see para 2-12).
CHECK VALVE. One-way valve prevents air from flowing out of supply air reservoir back
EXTERNAL AIR COUPLINGS. Tractor to trailer couplings are provided on M915, M916,
and M920 models. All models are equipped with front external air couplings for brake
use when the vehicle must be towed, Rear external air couplings are provided on M915,
M916, M917 and M920 for brake actuation of a disabled vehicle being towed.
PRIMARY RESERVOIR LINE. Carries air from primary tank to supply reservoir.
6. TIRE INFLATION AIR HOSE FITTING. Used in conjunction with the tire inflation
air hose and chuck.
ACCESSORY DRIVE. Provides power to operate compressor.
8. COMPRESSOR. Draws air from cleaner, compresses it, and directs it to supply air reservoir.
9. COMPRESSOR GOVERNOR. Opens unloading valve to vent air before compression
when pressure in supply tank is above 105-125 psi (724-826 kPa).
AlR DRYER. Air from compressor is dried and contaminants are removed before entering
SUPPLY AlR RESERVOIR. Receives compressed air from compressor.
2-66 Change 2