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 76 of 481
E
PRESSURE PROTECTION VALVE
– Performs two functions:
• Allows air pressure to build to 60-65 psi (414-448 kPa) before supplying
air to auxiliary air-powered equipment.
• Closes off auxiliary air system from other systems if an accessory fails
and prevents loss of air from secondary reservoir.
D
WET TANK RESERVOIR
– Performs two functions:
• Traps water in air reservoir to protect other air systems from freezing or
corroding.
• Stores reserve air supply enabling operator to make normal stops when
engine stalls or compressor fails.
TM 9-2320-272-10
Change 2
1-59
1-20. COMPRESSED AIR AND BRAKE SYSTEM OPERATION (Contd)
G
WET TANK RESERVOIR DRAINVALVE
– Provides a drain for moisture
and air from reservoir.
F
ALCOHOL EVAPORATOR (M939/A1 series)
– Helps protect air lines
from freezing (not used if ABS kit is installed).
B
AIR COMPRESSOR
– Draws in air from the intake manifold and forces it
into the brake system and wet tank reservoir.
A
AIR DRYER
– Installed in supply line to wet tank and removes moisture
from inlet air to wet tank (M939/A1 air dryer kit installed only), or (replaced
with new type for vehicles with ABS kit installed).
J
GOVERNOR
– Trips valve inside compressor to regulate flow of air to the
system.When pressure builds to 120-127 psi (827-876 kPa), the governor will
close valve.
I
EXPELLO VALVE
– Augments air dryer condensation blowdown by venting
moisture when compressor cycles (not used if ABS kit is installed).
C
SAFETY VALVE
– Located at the inlet side of the wet reservoir, it prevents
pressure build-up by releasing air pressure exceeding 150 psi (1034 kPa)
when the governor fails to regulate air supplied by the compressor.
H
AIR DRYER
– Removes moisture from inlet air to wet tank (M939A2 only)
or (not used if ABS kit is installed).
Back to Top
