I bought a used BAP and both the black insulated wires with red and black wires inside (resistor box, and pressure switch) were cut and individually soldered together. This makes the unit supply 17 volts at all times. I really would like to use a Hobbs 3 psi pressure switch, but I don't know which wire is originally intended for what since they were cut below the labels, and they are identical.
I performed a voltage test recommended by whoever answered my email over at KB. They said whichever red and black wires I unhooked that made it drop down to 12 volts would be the pressure switch wire. Problem is both of them let it drop down to 12 volts after I disconnected them. Which makes sense to me, since both do essentially the same thing except one is meant for a resistor box, and the other a pressure switch.
My exact test was as follows: The red fused BAP wire connected to the positive battery terminal. The BAP ground wire and negative multimeter terminal on the negative battery terminal. The positive multimeter terminal to the red unfused BAP wire. With both sets of red and black wires each twisted with their pair, I would get 17 volts from the red unfused BAP wire. When I would undo one red and black pair and reconnect, I would get a 12.7 volts that would drain down and hold at 12.2 volts. When I disconnected the red fused BAP wire from the positive side of the battery the voltage reading would very slowly drain down. The other one I would get a constant 12.1 volts, and when I disconnected it, it would quickly drain down. I'm not sure what to do at this point or if it even matters. A Hobbs pressure switch may work with either one but I'm not sure. Does anyone have a KB BAP not installed that they would be willing to test for reference?