Originally Posted by RogerSwann
If not having an air dryer is a safety issue, forget puzzling over why Jayco did not order them.
Why would Freightliner build them? The parts manager seemed to think a non air dryer version didn't exist. How many operators of the vehicles do not have air dryers? Plenty of these units in service, has the lack of a dryer been an issue?
For decades air brake-equipped trucks did without what are (modern) desiccant-style air dryers. Generally daily (especially in freezing weather) the driver had to manually drain the accumulated water and oil residue from the air tanks. Water forms when the air is heated and compressed into the air tanks where it then cools, condensing the moisture in the air. Oil is carried into the airstream by the air compressor which is engine oil lubricated. These liquids in the air are not what you want going through the air system degrading the internal components, and you especially don't want the water to freeze blocking a portion of the system and possibly creating safety issues. Before today's desiccant dryers some rigs had alcohol injectors to keep things from freezing.
Most of us here remember cars before ABS and we learned how to drive without it, but most can agree it does save lives. When you add the additional components to give an air brake-equipped truck ABS (like a Seneca) you add numerous additional pieces that can (eventually) malfunction because of contaminated air. A properly working air dryer will likely extend the lifespan of those components. Why aren't newer Seneca owners having issues? In my opinion it is likely because those units are still fairly "new", and most RV owners don't drive them extensively in sub-freezing weather. But 10+ years out I wonder what things might look like? Those brake control components that corrode and fail will be very expensive to diagnose and replace.
I spent my career in a municipal fire department, the trucks we had when I started on the department did not have air dryers. Every day we drained the air tanks at shift change, and twice a day we did it when it was below freezing. You would be shocked at what comes out of an older truck! Those older trucks without ABS had brake components that would fail periodically, including the air tanks failing because of rusting through from the inside! Once we started ordering any new trucks with air dryers and retrofitted the older trucks, problems such as those decreased significantly. Once ABS became available on fire trucks, air dryers were standard equipment to protect the components of the ABS system from contamination.
In my opinion this is a case where I believe Jayco is "penny-wise and pound-foolish" on the backs of current owners who will absorb the higher maintenance costs later. To build a truck with a modern air dryer might cost just a few hundred dollars. Considerably less than what it will cost to replace just one air brake ABS modulator valve down the road. If I had an air brake Seneca I would definitely install an air dryer, and I probably will anyway even though I have a hydraulic brake unit to better protect my suspension leveling valves, parking brake, and engine cooling fan components.
Does an air dryer add an additional maintenance step? Yes. But I think the costs of periodic desiccant cartridge replacement outweigh the other possibilities 10+ years down the road.