TM 9-2320-272-24-1
1-23. COMPRESSED AIR AND BRAKE SYSTEM OPERATION (Contd)
Key Item and Function
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 CHECKVALVE -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 NO. 1 - Serves two functions:
Allows system to receive signal pressure from either pedal valve or, when towed, from brake
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system of towing vehicle.
Serves as a tee between front and rear primary signal lines.
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H SECONDARY AIR RESERVOIR DRAINVALVE - Provides a drain for moisture and air from
secondary air reservoir.
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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 NO. 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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