I doubt it is the switch if it is comming on early and staying on, It sound like your grounding out somewere. Check the negative wire to be sure non of the insulation is stripped off anywere and grounding. If those switches were to have a failure it should only be failure to move the switch to the closed circuit position. I don't think we had but maybe one switch returned in 2 years. It's a good ideal to loom your wire in case you have not to keep them protected.
Anouther thing is to check your hose going to the
pressure switch, Make sure there are no obstructions in it. It it has say a chunk of carbon from the motor in it and it is causing a obstruction it will create a higher pressure, just like a nozzle does at the end of the hose making the switch open early because it sees the correct psi.
