SERVICE MANUALFig. 5 Typical Air System Schematic with ModularControl Valve1Exhaust Port2Spring Brake Chamber3Delivery-Tractor Port4Auxiliary Air Delivery5Secondary Reservoir6Reservoir #2 Supply Port7Reservoir #1 Supply Port8Primary Reservoir9Delivery-Trailer Port10Tractor Protection ValveThe parking brake valve (yellow knob) controls thespring brakes on the tractor and when exhausted,simultaneously causes the trailer supply valve to trip andexhaust, thus applying both tractor and trailer parkingbrakes as required by Federal Regulations. The trailerbrakes may be independently released by pushing onlythe trailer air supply valve (red knob) in.OPERATIONInitial ChargeWith the system completely discharged, both knobsare out (Fig. 6). When system pressure reaches 448kPa (65 psi), the red knob (trailer supply) may be pushedin (Fig. 7) and should stay in, charging the trailer systemand releasing the trailer brakes. The yellow knob (systempark) may now be pushed in (Fig. 8 ) which will supply airto the tractor spring brakes, releasing them.System Park (Fig. 6)With both knobs in for normal tractor-trailer, runmodes, the parking brakes on, both tractor and trailer’may be actuated by pulling the yellow knob out, whichexhausts the air from the tractor spring brakes andsimultaneously causes the trailer supply valve to pop out,applying the trailer brakes. This complies with FederalRegulations that one control must apply all the parkingbrakes on the vehicle.Fig. 6 Total Vehicle ParkedFig. 7 Charge Trailer with Tractor ParkedLegend for Figs. 6, 7, 8 & 91Trailer Supply2Parking (Spring) Brake3Modular Control Valve4Trailer Emergency5Tractor Protection Valve6Trailer Emergency7Quick Release Valve8Spring Brake Chamber9Tractor Spring Brake Control10Secondary Reservoir11Primary Reservoir12ExhaustCTS-4079 - CHAPTER VII - Page7
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