Abstract: A compressed air system includes an electronic control which controls enabling and disabling of the compressor in response to pressure level variations in the system storage reservoir. A humidity sensor is installed in the system reservoir and generates a signal which varies as a function of the humidity of the compressed air in the reservoir. The control unit includes a comparator which compares the signal generated by the humidity sensor with a reference signal and generates a humidity control signal when the humidity of the air in the reservoir exceeds the reference level. The control unit responds to compressor disabling by causing the system air dryer to regenerate or purge for a predetermined time period, even if the compressor is unloaded for time periods greater than the predetermined time period.

Abstract: An electropneumatic subsystem of a vehicle compressed air braking system controls communication within the trailer control line, the trailer supply line, and the tractor spring brake delivery line. A valve operated by pilot pressure is installed in the trailer control line, and responds to the pressure level in the trailer supply line to open or close the trailer control line in accordance therewith, thereby providing a tractor protection function. A solenoid valve in the trailer supply line is actuated by an electronic control unit to open and close the trailer supply line to thereby perform a trailer spring brake control function and tractor protection function.

Abstract: A fluid pressure braking system for a vehicle having service brakes and spring activated parking brakes includes electropneumatic activators for effecting and holding a limited service brake application while the driver leaves the vehicle to make a route pick-up. Accordingly, the spring brakes are not used during route pick-ups, thereby increasing the life of the spring actuator since it is not repeatedly cycled. An electropneumatic interlock automatically effects a parking brake application if the vehicle ignition is switched off while an electropneumatic service actuation is effected.

Abstract: A compressed air system includes an electronic control which controls enabling and disabling of the compressor in response to pressure level variations in the system storage reservoir. The control unit responds to compressor disabling by causing the system air dryer to regenerate or purge for a predetermined time period. The timing period of a charge timer is initiated when the compressor is enabled. When the charge timer has timed out, the compressor is disabled and the air dryer purged for the predetermined time period.

Abstract: A compressed air system includes an electronic control which controls enabling and disabling of the compressor in response to pressure level variations in the system storage reservoir. The control unit responds to compressor disabling by causing the system air dryer to regenerate or purge for a predetermined time period, even if the compressor is unloaded for time periods greater than the predetermined time period. If the compressor comes back on load before expiration of the predetermined time periods, purging of the air dryer is immediately discontinued. Accordingly, the air dryer is never purged for long periods of time, thereby conserving the desiccant used in the air dryer, and also increasing the efficiency of the engine which operates the air compressor, since turbocharged engines normally communicate the output of the turbocharger to the air compressor, and venting a portion of the turbocharger for long periods of time can significantly decrease engine efficiency.