You must have 12 volts at the pump to keep these pumps running the way they should when you supply less than 12 volts and use under gauge wire. You create dirty voltage. Lower Voltage means Higher amps & spikes. Now you are cooking the Pressure Switch because the PS is rated at 15.1 amps. When you get on and off the gun, it keeps pressuring until it turns off. Doing this over and over creates heat in the line. This is what is causing the PS to burn up. PS can’t take the load and takes a dump. This is why the dwell setup works better. in our line of work. Handles more amps. I did see Amazon had some Micro Switches in 25a ones but only 2 wire connections. You have to use better wire to bring down the amps and you shouldn’t have any issues. My pumps always ran for a year.