[Glenn and Laureen]

Hello, everyone. Glenn Parker, of Austin TX, here with my first post. My wife (Laureen) and I recently bought a 1984 Newell 35' coach that had been posted on this site by the previous owner in Gridley, CA. My wife's BIL (Clarke Hockwald) is a member of this forum and helped us evaluate the coach thoroughly before the purchase and we are very happy with it. Put new tires on it in Gridley and had a little maintenance done at All Aboard America in Mesa, AZ before heading home to Texas. One thing that is puzzling me is that I don't know the function of one switch in the center console that seems to be related to the house air system (all the leveling switches are right there). It is unmarked and is the bottom switch in the photo (or the far right, depending on how the photo appears). I have had the switch in both positions and can't seem to tell any difference in operations. Any ideas as to its purpose?