OperationAir DryerThe function of the air dryer is to collect and remove moistureand contaminants before the compressed air reaches the airreservoirs. This protects the air system components frommalfunctioning including blockage, corrosion, and freezing.For air tank draining requirements, refer to the MaintenanceInstructions section as well as local regulations.The air dryer is installed in the discharge line between the aircompressor and the air system reservoirs. The air dryer includesa replaceable desiccant cartridge and oil blocking filter that isperiodically serviced. It also may include a heater to prevent thedischarge valve from freezing in cold weather.Trailer Brake Hand ControlWARNINGTo prevent property damage, personal injury, and/ or death, the hand control valve should never beused to apply the trailer brakes when the tractorand trailer are parked. Air pressure may leak fromthe system, and the vehicle could roll away.The trailer brake hand control is used to apply the trailer servicebrakes, independently of the tractor service brakes. The trailerbrakehandcontroloperatesavalvethatprovidesgradualcontrolof air pressure applied to the trailer service brakes. The trailerservice brakes can be fully or partially applied, but when in apartial position, can be overridden by pressing fully on the brakepedal.To apply the trailer service brakes utilizing the hand control,move the lever clockwise (down). The further the handle ismoved clockwise, the greater the air pressure applied to thetrailer brakes. The trailer hand brake handle will remain inplace with the desired brake pressure applied until the handleis manually moved. To release the trailer brakes, move handlecounterclockwise (up) until trailer moves freely.Trailer Air Supply and Parking Brake Modular Controls• TRAILER AIR SUPPLY (RED octagonal knob)• PARKING BRAKE (YELLOW diamond knob)186
