[77newell]

There are 3 groups of air users on my 93 coach; the leveling system, the brake system, and all other users. There are ways of identifying which group(s) are leaking.

As Tom said, if a brake gauge needle is dropping at the same rate as the supply gauge then you have a brake system problem.

Underneath the coach just ahead of the drive axle are a couple 1/4 turn valves. One supplies the leveling system, the other supplies all other users. Shut the valves and check the dash "supply" gauge and the gauge at the rear 6-pack for the leveling system. The dash gauge will show the leakage rate for all other users and the 6-pack gauge will show leakage rate for all of the leveling system.

I think the newer coaches also have a lower pressure system that is fed from the "all other users" supply. This low pressure system feeds the toilets and maybe the slide seals. Others on this site will know. Anyway, there should be a shutoff valve on the feed to this system followed by a pressure gauge. Isolating this system and watching the gauge wii show leakage rate.

Finally, there is one more leak source not yet covered, the 120VAC compressor system itself. If your leakage rate with the engine running is much slower than with the 120VAC compressor then some ting in that compressor system is leaking, usually the dryer though not always.

I have now exceeded the limits of my knowledge and will shut down