[Richard]

Sorry but I have to ask some dumb questions.

Have you ever aired it this way? In other words has it worked in the past OR this is the first time you have tried this.

Second do you have the double air line situation that Gary showed in the pictures above?

Third, are you trying to feed air through the air pressure doubling device?

[johnkosir]

712 will air up that way, air goes through a water separator through probably 3/8 braided hose to engine air drier mounted behind drivers side tag through 3/8 plastic air line through check valve and into my 120v compressor air tank (back one) but I have a 12v compressor, I think you have 2 120v compressor's

[DK on the road]

Thanks for responding Richard,

Have you ever aired it this way? In other words has it worked in the past OR this is the first time you have tried this.
It has worked in the past. This is the normal way I have always hooked it up.

Second do you have the double air line situation that Gary showed in the pictures above?
Not sure about the the double air line. I have a 3/8 blue feed with a directional check valve feeding air to the manifold and the air doubler and pneumatic tool outlet. Then a 1/4" black resupply line with a directional check valve sending air back into the tanks and the system. I did have a check valve not working and I replaced both. This is where I may have created a problem and not getting them installed correctly. While replacing them, I installed the one on the 3/8" wrong because I wasn't able to fill tires from Pneumatic fitting.  I have since reversed it.
When it was reversed, and I added air into the coach the brake air pressure would rise and the coach air would not go up.

Third, are you trying to feed air through the air pressure doubling device?
No, I'm adding through the pneumatic tool line

[Richard]

I think you answered your question. The sequence of events, it worked, i touched something
, now it doesnt work.

Seriously, think your way through how the air is supposed to flow.