[77newell]

IF you are willing and assuming your coach is plumbed as my 93 is there is a step you can take to begin to locate the leak. On the bulkhead ahead of my rear axle are two ball valves, one controls air flowing to the front the of the coach and the other controls the air flowing to the rear of the coach. If you shut off those valves and monitor the "supply" pressure gauge (that gets its signal from the front air distribution block) and the pressure gauge on the rear six-pack that monitors air supply for the rear of the coach, you may be able to determine where in the coach to look for leaks.

It would seem that you do have a leak somewhere in the left rear air suspension system.