COMPRESSED AIR AND BRAKE SYSTEM OPERATION I
The compressed air and brake system takes filtered air, compresses it, and supplies it to various components that
enable the operator to slow down or stop the vehicle. This system also supplies compressed air to air-actuated
accessories throughout the vehicle. These components and accessories will be described as part of the following
Medium Wrecker Automatic Brake Lock System Operation (page 1-57).
Air Pressure Supply System Operation (page 1-58).
Secondary Service Airbrake System Operation (page 1-62).
Spring Airbrake System Operation (page 1-64).
Primary Service Airbrake System Operation (page 1-65).
Auxiliary Air-Powered System Operation (page 1-68).
Air Venting System Operation (page 1-70).
Central Tire Inflation System (CTIS) (M939A2 series vehicles) (page 1-72).
Medium Wrecker Automatic Brake Lock System Operation.
The M936/A1/A2 Medium Wrecker Automatic Brake Lock System locks the service airbrakes when the
transfer case power takeoff lever is engaged. Major components of the automatic brake lock system are:
TRANSFER CASE POWER TAKEOFF LEVER - Opens the brake lock control valve through mechanical linkage
BRAKE LOCK CONTROL - Allows air pressure to flow from secondary air reservoir to pressure regulator and
activate variable speed governor.
PRESSURE REGULATOR - Reduces and regulates system air pressure to 70 psi (483 kPa) for automatic brake
TREADLE VALVE - Connects pressure regulator and service airbrakes.