So I just acquired a 1996 "Monarchgency" (a coach that by the year and specs should be a Monarch, but was badged as a Regency; there have been a few of these) - Spartan chassis, Cummins M11 engine, 38' coach - it has an odd air leak.

Inside the generator bay, up to the right, there's an air fitting - the nipple facing forward just constantly vents air when the coach is powered. It looks like something should attach to this nipple, but everything that needs air works, and the coach does build and hold air, and I can't find a dangling air hose. This fitting is constantly venting air and this seems like not how it should be.

Does anyone know what should be attached to that front facing fitting? Seems like this could be a somewhat simple DIY fix and I'd rather not pay $200/hr to fix something super easy. Everything works so it's a real mystery!

If it has two wires going to it then it is the air suspension dump valve. Also spray some soapy water around the brake treadle valve as those tend to leak where the two halves mate. Ours has failed twice…
Good luck
Billy T

Oh, another thing, our coach came equipped with an air powered vacuum generator for the dash HVAC. That thing would pass air through, non-stop until the pressure reached the setting of the protection valves, 60-70 psi. I replaced ours with a 12v vacuum pump from a 90’s Ford diesel pickup that performed the same task. Mounted it in the run panel on a Switched 12v circuit. It’s been that way for 20-years.
Billy

I'll have to post a picture of it, I suppose. I don't think it's related to the dash A/C as it vents air continuously when the coach is powered up. It really looks like there's simply a missing hose but I can't locate one that's disconnected.

It's a strong current of air, too!

Could it possibly be a fitting to attach an air hose to inject air into the brake system? This would be used when the coach cannot generate air pressure and the coach needs to be moved (ie. towed). The injected air would release the brakes.

The leaking air would be a fault that should be corrected.

Here is a picture of the leaking fitting. That nipple pointing directly out in the near center of the frame just vents air continuously. Looks like a hose should be attached but I'm not sure. Would be nice to be able to self fix.