TM 9-2320-272-10
1-20.
COMPRESSED AIR AND BRAKE SYSTEM OPERATION (Contd)
(2)
The secondary constant pressure system is made up of the following components:
A
LOW AIR PRESSURE SWITCH - Activates warning buzzer and warning lights when air pressure goes below 60
psi (414 kPa).
B
PEDAL VALVE - Allows air pressure from secondary constant pressure system to flow into secondary signal
system when operator depresses brake pedal.
C
SECONDARY AIR PRESSURE GAUGE - Indicates amount of air pressure in secondary system.
D
ONE-WAY CHECK VALVE - Allows air pressure to flow into secondary reservoir but prevents it from coming out if
constant pressure system fails or engine stalls.
E
SECONDARY AIR RESERVOIR - Stores enough air pressure so the operator can make five normal brake
applications before running out of air if constant pressure fails or engine stalls.
F
INTERMEDIATE REAR BRAKE CHAMBERS - Converts air pressure to mechanical force which applies
intermediate rear service brake.
G
DOUBLECHECK VALVE #1 - Serves two functions:
•
Allows system to receive signal pressure from either pedal valve or, when towed, from brake system of
towing vehicle.
•
Serves as a tee between front and rear primary signal lines.
H
SECONDARY AIR RESERVOIR DRAINVALVE - Provides a drain for moisture and air from secondary air
reservoir.
I
FRONT RELAY VALVE - Boosts signal air to rear brake chambers; regulates air pressure to rear brake chambers
so operator has control over amount of braking; and releases air pressure to rear brake chambers directly to vent
when brake pedal is released.
J
STOPLIGHT SWITCH - As the brake pedal is depressed, switch receives an air pressure signal at electrical
contacts which close to activate circuits to taillights.
K
DOUBLECHECK VALVE #2 - Allows either primary or secondary signal air pressure to activate stoplight switch
while keeping the two systems separate.
L
REAR-REAR BRAKE CHAMBERS - Converts air pressure to mechanical force which applies rear-rear brakes.
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