[77newell]

Jon's solution would make sense given the symptoms, but it would also suggest that if you have a leak in the stuff connected to the supply system it would drain one or more of the brake tanks and bring you to a halt when the pressure gets low enough to engage the spring brakes. Every diagram I've seen from the system vendors (Bendix for example) have shown the two brake tanks being fed by the supply tank through check valves. In that scheme the only way the brake tanks can get air is from the at least somewhat higher pressure in the supply tank. Therefore in those schemes; no pressure in the supply tank means no ability to pressurize the brake tanks.

Given what I've just experienced with my water compartment hose connection it may be worthwhile considering that the factory connected the tanks incorrectly in which case what Jon has suggested is as possible cause of your problem. If you have truly verified (and I am in no way challenging what you are reporting Larry) there is no pressure in the supply tank via testing tank drain, pocket doors, toilet and etc then your system must be configured "uniquely" and you will need to get the check valve feeding that tank functioning correctly. While not urgent I prefer to have the system reconfigured to operate in the standard fashion if only to help mechanics in the future sort out problems I may have in the future.

Larry, I hope this helps, send me a message and maybe we can talk if need be.