In the charge cycle, the compressed air flows into the air brake dryer through the supply port (SUP/11) where baffles change the direction of the air flow several times. This constant changing of air flow reduces the temperature and allows the contaminants to condense and drop to the bottom of the air brake dryer end cover. The air is then directed through a desiccant cartridge, where water, oil, and other contaminants first flow through an oil separator. The separator removes the water in liquid form as well as oil, oil vapor, and solid contaminates. Air then exits the oil separator and flows through the column of desiccant. The air becomes progressively dryer. The majority of the dry air exits through the internal check valve into the delivery port (DEL/2) and out to the supply reservoir.

In the purge cycle, the air compressor unloader port is connected to the air brake dryer control port (CON) which opens the purge valve in the bottom of the air brake dryer. This allows the water and contaminants to exit through the exhaust post in the bottom. Contaminants are blown out by air stored in the air brake dryer housing during the charge cycle. The complete purge cycle takes about 15-30 seconds.