AIR BRAKES - GENERAL INFORMATIONFigure 20 - 6x4 Tractor With Trailer Towing Provisions and Initial Split Air System With ModularControl Valve For Spring Brake and Tractor Protection ControlOperationFigures 21 and 22 illustrate the power divider lock controlconnection at the instrument panel since the introductionof FMVSS 121.Figure 21 illustrates three separate control valves (springbrake, tractor protection and power divider lock) used atthe instrument panel. Figure 22 illustrates the powerdivider lock used with the modular control valve. Positiveidentification of the power divider lock system can bedetermined by installing an air test gauge in theair line to the power divider lock. Build pressure in thesystem, operate the valve and observe the air test gaugeto determine which mode has air pressure. If airpressure is recorded on the air test gauge when thepower divider lock is positioned in the lock mode, youhave a CONDITION 1 or CONDITION 3 power dividerlock. (Power divider lock is air actuated and springreleased.) If no air pressure is recorded at the air testgauge when power divider lock is positioned in the lockmode, you have a CONDITION 2 power divider lock.(Power divider lock is spring actuated and air released.)CTS-4154Y - Page 18
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