How do check a pressure switch to know if its bad?

What is specifically going on that makes you think the pressure switch is bad. Lo or high pressure? Straight cool a/c or heat pump. In cooling or heating?

Do you have a set of manifold gauges and/or EPA certified by chance?

Access to an ohmmeter?

Question, How do check a pressure switch to know if its bad?

Answer,, if you don`t have correct tools, you can remove wires from pressure switch, jumper them together with a short piece if wire, ( do this briefly and just to test only, don`t operate furnace ,switch is a safety device "very important", for testing only) if furnace starts up and works you no the PS is bad,, again replace PS before using furnace