AIR BRAKES - GENERAL INFORMATION3.With hand control valve, parking brake controland tractor protection control (TRAILEREMERGENCY) in released position, the airgauge at emergency coupling should have airpressure corresponding to that of air gauges incab. The air pressure at service coupling willremain at zero.4.Apply service brakes using the foot valve; the airgauge at service coupling should indicateapproximately the same pressure as the gaugesin cab, +41 kPa (+6 psi). Release servicebrakes. Air pressure at the service couplingshould drop to zero, while the air pressure atemergency coupling should correspondapproximately to that of air gauges in cab.5.Pull tractor protection control valve (TRAILEREMERGENCY) out. Air pressure should drop tozero at air test gauge on emergency coupling.Then push valve in and air pressure should raiseto that of air system of vehicle. No air pressureshould be recorded at service coupling.6.Check hand control valve operation by movinghandle from released position to appliedposition. As the handle is moved toward appliedposition, air pressure at service brakes shouldgradually increase. At full applied position the airpressure should be the same as chassissecondary system. Then move control handle toreleased position and air pressure at servicebrake connection should drop to zero. The airpressure at emergency coupling shouldcorrespond to that of air gauges in cab.7.Pull parking brake control out. Air pressure atemergency connection should drop to zero.Push control knob in. Air pressure at emergencycoupling should raise to that of main air system,while air pressure at service coupling should notraise. If the foregoing checks perform asdescribed, the chassis is ready for service. If thechecks do not function properly, a more detailedcheck of components will be required. Refer toCOMPONENTS Section for detailed informationregarding service check on various components.CTS-4154Y - Page 22
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