TM-9-2320-272-10
TRUCK, 5-TON, 6X6, M939, M939A1, AND M939A2 SERIES TRUCKS (DIESEL)
TECHNICAL MANUAL; OPERATOR'S MANUAL
SEPTEMBER 2004
CHANGE 2
TM-9-2320-272-10 - Page 81 of 481
TM 9-2320-272-10
1-64
1-20. COMPRESSED AIR AND BRAKE SYSTEM OPERATION (Contd)
d. 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:
B
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.
A
SPRING BRAKE WARNING LIGHT SWITCH
– Activates warning light
when spring brakes are engaged.
C
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.
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