[hypoxia]

If your coach is plumbed similar to mine it has a separator valve in the outside rear right compartment with a bunch of pneumatics in it. If you close that valve it isolates the house from the chassis. Then you can watch the pressure gauge in that compartment as well as the gauge in the compressor compartment to see the air leakage in either system. The gauge in the air compressor compartment will show chassis leakage, the gauge in the rear right compartment shows leakage in the house. In my diagram I called that valve "Separator Ball Valve In Rear Compartment"