TM 5-2330-305-14
c. Service Diaphragm. Counteracts the emergency diaphragm to provide service
brake application. It is connected to the pushrod and controlled by the relay quick
release valve. As pressure is applied to the diaphragm, the pushrod extends to
apply force to brakes.
1.3.5.5 AUXILIARY SERVICE RELAY. Speeds up application and release of brakes on
auxiliary towed trailers by shortening the length of tubing which air must pass from
the brake valve. As primary brake system pressure increases, the relay opens
allOWing emergency system pressure to supply the secondary service system.
1.3.5.6 HEIGHT CONTROL VALVE. Maintains constant chassis ride height by
determining distance between chassis frame and wheel axle. The valve opens to add
or remove air in air bags.
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