COMPRESSED AIR AND BRAKE SYSTEM OPERATION (Contd)
Spring Airbrake System Operation.
The spring airbrake system applies rear brakes when vehicle parking brake is applied or in event of a major
brake failure. The spring brake is located on one of the two service brake chambers at each rear wheel. Major
components of the spring airbrake system are:
SPRING BRAKE WARNING LIGHT SWITCH - Activates warning light when spring brakes are engaged.
SPRING BRAKE RELEASE CONTROL VALVE - Pushed in to release spring brakes independently of mechanical
parking brake. Control is also used to release spring brakes in order to test and adjust mechanical brake.
DOUBLECHECK VALVE #4 - Allows spring brake air pressure to come from either release control valve or spring
parking brake valve directly to doublecheck valve #3.