Testing for pressure switch failure on your 12 volt diaphragm water pump is an easy operation. If you have a 240 volt model diaphragm pump, print these instructions and give them to a qualified electrician with the pump for them to check it for you.
Step 1: Disconnect your 12 volt water pump from the power supply.
Step 2: On the end of the 12 volt water pump end is a black square box. This is the pressure switch. Take off the cap on the pressure switch. If the cap has a screw in the middle of it use a Phillips head screwdriver to remove the screw and take off the cover. (This is for the FL range of Escaping Outdoors pumps). Other brands will be similar to do.
Step 3. Check again the power is disconnected. Slide out the two contact wires from the pressure switch and touch them together. Best to wrap them in electrical tape.
Step 4. Connect the 12v water pump to the power supply again. Don't worry if water is not connected - the pump can run dry for a short period as you only need to turn it on for a few seconds to test. If the pump motor runs, disconnect immediately from the power supply.
Step 5. If the pump now runs the water pump motor is fine and you need to replace the pressure switch. If the pump did not run then the problem lies elsewhere.
If your pump is newly installed and you heard it running in a noisy or bumpy manner then you probably have a pump which is too big for your system. This can be fixed by adding a pressure tank, dropping the PSI on the pressure switch ( see related FAQ ) or by using a different 12 volt water pump better suited to your application.
Other articles relating to this question are:
1. Do I need a pressure tank or accumulator tank? Check out Water Pumps Now article here.
2. How to adjust the PSI on my 12 volt water pump pressure switch. Check out Water Pumps Now article here.