Tom-
Sorry to take awhile getting back to you.
If you stick your head under the right front "fender" (in front of the entry door), straight above you is the regulator setup, bracket-mounted to the horizontal frame component. It is a two-component fixture and not very big. I will attach herein (I hope) a graphic of it out of my owner's manual. In the following, when I say "right" or "left" I refer to the coach with driver's side being "left". The left component as you gaze up under the front cap is black with what appears to be a large knob on the bottom, which may be the means of pressure adjustment - my book doesn't explain that, unfortunately. The second and smaller diameter component is brass, and the black hose to the door comes out of it on the right.
That approx. 3/8" hose on my rig splices to a 1/4" hose mid-loop, and that goes up to the door and seal via a hole in the stepwell. A brown plastic? hose feeds unregulated air into the black component and routes in from a bundle of wires and hoses above the horizontal frame. You could have a leak anywhere, from wherever that brown hose comes from to the door seal itself. I'd start by checking the easy stuff - the hose fittings on either side of the regulator including the splice between the 3/8 and 1/4 " hoses. They are the most in harm's way; a road hazard/rock/stick could have dislodged or loosened a hose.
I'd do that before messing with the regulator adjustment, but if necessary, I spose one could disconnect the 3/8" hose at the union/splice and adapt a pressure guage to it (preferrably via a long hose so you aren't under the coach while testing). Your guage will have to be able to clearly distinquish between 3-5 psi, though. Hope you don't have to disassemble the door to check the hose fitting in there. My book says the air seal is one piece on the '06 Monterey, so a micro tear anywhere could be the culprit. But as I recall you've been working on the auxilliary compressor or vacuum pump lately? I'd check that out first, though I'm sure the door seal air comes from the main tanks, not the little compressor. You may have inadvertantly snagged and loosened a hose.
In the diagram below (shown as if looking toward the coach from the front), the brown hose is on the right, enters the larger component which is actually black and has the large knurled knob on the bottom, then that connects to the brass component with the two wires, and the 3/8" hose comes out of that on the left and ultimately to the door seal. My guess is that the black knob is the pressure adjustor, and the two wires turn the valve inside on or off as determined by engine/tranny activity.
(Note the frame-mounting bracket is actually configured above the black component, not to the side as illustrated.)
Hope this is of some help.
Joel
