I'm learning a little about pneumatic switches. The "P" port is Pressure Inlet. The "A" port is Pressure Out. The "R" port is Pressure Release.
I'm guessing that one of the 1/8" lines is Pressure In and the other is Pressure Release. Now how to sort out which one is which? Absent better advice, I'll hook them up and see if it works. If it doesn't, I'll reverse it.
Well if you start the truck, as soon as the wet tank exceeds ~85PSI, the supply line will start to flow air...
For cab suspension, one of the lines is supply pressure from the wet tank, the other line is out to the cab suspension height control valve. The R port Vent is on the back of the hydraulic control valve module and does not have a line attached to it...
Think of the cab valve like a single pole double throw switch that switches a common connector between two other connectors. Supply pressure comes in on one of the two switchable connections(P), the load/cab suspension is on the common connection(A) and the second switchable connection is the vent or release port(R).
A switches between P and R. When you switch the valve to the P port, pressure flows in thru p and out the common port A to feed the load, and the ride height valve uses this pressure to inflate or deflate the bags to control height. When you switch the A from P to R, this seals the P port and connects the A port to the R port, and any air in the cab suspension flows back and vents to atmosphere thru the R port... In my picture you can just see a sintered bronze filter in the R port where the air vents out when deflating the system. this is to keep debris and insects out of that port...
