How the Air Brake System Works

All air brake systems use air pressure to apply the brakes when you step on the pedal. The air is stored in a series of pressure tanks on the motorhome. The air is pressurized by the air compressor, located on the engine, and operates only while the engine is running.  Clean, filtered, turbocharged pressurized air from the intake manifold is force-fed into the air compressor and the pressure is regulated by the air governor. Most, if not all systems, work on 120 psi of pressure.

The air then passes through the air dryer, which filters and dries the compressed air to keep it from freezing in the winter time and from causing general corrosion of the air system.  There are two primary filters in the air dryer which must be serviced.

• The desiccant cartridge which removes moisture and oils in the compressed air.
• The coalescing filter which removes any particles still remaining in the compressed air.

From the air dryer the compressed air is sent to the "wet tank" and on to the front and rear brake tanks. This treated air can  now used for the braking and other operations of your coach.

An important servicing item in your maintenance schedule is to service the air dryer.  The air dryer cartridges must be changed on a regular basis or the desiccant will break down and contaminate the air system. A service kit is available that has both the desiccant and the coalescing filter cartridge.  If the filter and desiccant cartridge get saturated with moisture and oil from the compressor, or breakdown with age,  it will clog the dryer and/or cause the purge valve to stick open. When this happens, the air system will not build up pressure. This contaminated air will get into the wet tank and on into the system valves where many other problems will occur. 

I hope this helps you to understand the basic air system and what will happen if the air dryer is not serviced on a regular basis.