Goose, I did look it up. I can't find squat about PM of the air drier / desiccant renewal in the shop manual. There are schematics and instructions on how to remove and replace the drier from the air supply unit (it's built into it of course, along with compressor, valves, etc.), but no mention anywhere of how often it should be serviced. My guess is: not until it's broke. :wink: