What is the function of the air dryer?

The air dryer sits between the compressor and the storage tanks. It removes water vapor and oil mist from the compressed air before that air enters the system. By drying the air, it reduces the risk of water freezing in lines, prevents corrosion in tanks and valves, and extends the life of brake components. Air dryers contain a desiccant cartridge that absorbs moisture; the cartridge is automatically regenerated during the governor's unloaded phase by purging trapped moisture out of the system. The desiccant cartridge eventually wears out and must be replaced as part of scheduled maintenance. If you see oil or water collecting in the supply tank despite the air dryer, the dryer or its purge valve may need service.