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 89 of 481
TM 9-2320-272-10
1-72
Change 2
1-20. COMPRESSED AIR AND BRAKE SYSTEM OPERATION (Contd)
B
ELECTRONIC CONTROL UNIT (ECU)
– Contains CTIS selector panel so
that operator can change tire inflation during vehicle operation.
A
PNEUMATIC CONTROLLER
– Directs air pressure according to ECU
commands.
D
AIR DRYER AND FILTER
– Separates moisture from compressed air system
and filters impurities from compressed air before they enter CTIS.
G
SPEED SIGNAL GENERATOR
– Signals ECU to automatically inflate
CTIS when vehicle speed exceeds the top speed setting for the selected mode
by 10 mph (16 km/h).
E
EXHAUST VALVES
– Exhausts air from tires during deflation.
F
WHEEL VALVES
– Isolates air pressure in the tires during normal
operation and for tire removal.
C
AIR PRESSURE SWITCH
– Protects air brake system for a minimum
supply of 85 psi (586 kPa) of air.
h. Central Tire Inflation System (CTIS).
NOTE
Vehicles equipped with antilock brake
system (ABS) will have a new air dryer
installed in position D shown below.
The CTIS is common to all M939A2 series vehicles. This system maintains tire
air pressure depending on which road type is selected. If this setting is changed,
tires will automatically inflate or deflate to the new setting.
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