TM 9-2330-373-14 & P
1-14. AIR MOUNTED FIFTH WHEEL KINGPIN SYSTEM (cont)
Pressurized air flows through the check valve, through the height control valve and into the air springs.
The height control valve regulates the amount of pressurized air required to take care of the varying semitrailer loads.
Air is regulated through the valve any time the semitrailer air system is coupled to the charged air system of the towing
vehicle.
Loss of air pressure or air spring deflection by off center loading will cause the actuating arm of height control valve to
move up. This up movement opens intake valve and allows supply air to pass through to air springs.
Down movement of the actuating arm opens exhaust valve, allowing excess air pressure to vent to the atmosphere.
A safety check valve in the intake fitting prevents pressure loss in the event of loss of supply air pressure.
A five-second time delay is built into the height control valve to prevent unnecessary actuation while driving on uneven
terrain at operating speeds.
Valve hunting action is eliminated by a 3/8-inch dead zone built into the valve.
When the semitrailer is uncoupled from the towing vehicle, the fifth wheel plate will drop or sag.
1-30
