THEORY OF OPERATION - CONTINUED
BRAKE SYSTEM - CONTINUED
The warning light and buzzer inside the cab are activated if air pressure drops below 64 psi (441 kPa) in either brake
system. If this happens, check air pressure gages to determine which system has low air pressure. Although vehicle
speed can be reduced using the foot brake control pedal, either the front or rear service brakes will not operate, resulting
in a longer stopping distance. Bring vehicle to a safe stop and have the air system repaired before continuing.
If the primary brake system becomes inoperative, the spring parking brakes automatically apply when air pressure drops
to 35-45 psi (241-310 kPa).
The vehicle has a four-channel anti-lock brake system (ABS) and cam-operated service brakes with non-asbestos brake-
The M915A3 has automatically adjusting slack adjusters. On all axles, brake chambers have a stroke alert indicator
which allows the operator to monitor brakeshoe wear.
REAR AXLE SPRING