Jabsco pressure switch

[mparent]

I have a jabsco fresh water 36950 pump. I replaced wiring and have power to pump. If if connect directly bypassing pressure switch the pump works. I tr5ied replacing the pressure switch but cannot get ot to work. The pump has two black wires. According to diagrams the positive wire from breaker switch goes to pressure switch and one black wire as well. the other black wire connects to the negative wire coning from the breaker. I assume since the black wires coming from the pump are identical that either wire can connect to the pressure switch. am I wrong? If so how can I determine which back wire from the pump is the negative wire?

[Blue Stocking]

The 1-way valves in the pump render the rotation un-important. I have 2 of these in Blue, and don't recall having to sus out the rotation question.