Tom,
I have a complete electrical book on my 06 PT, don't know if there are actual air system schematics still available. About the only way to find air leaks is to raise the coach up as high as it will go and block the frame up for safety. Then get your spray bottle with soap in it and start spraying every air fitting, air tank, air bag and anything else that has air in it. These were put together with the push to connect DOT air fittings which tend to leak after a few years of use. I have had to take apart many of these and cut off about a 1/2' of tube and stick it back together, usually solves the leak.