When you turn on the faucet or shower, you expect a smooth flow of water. In a private water system, the water is pulled out of the well with a pump and delivered to the faucets via supply plumbing. The pressure switch's job is to monitor the pressure in the plumbing and turn the pump on and off to maintain a preset level of water pressure. If this device malfunctions, it can damage the pump by accelerating its on/off cycles.
Remove or open the drain stopper in a sink. Turn on the faucet and allow the water to run.
Locate the well's pump. Some pumps are in the basement close to the pressure tank and pressure switch. If you can't find the pump, it is probably installed inside the well.
Listen to the pump to determine how often it cycles on and off. If the pump cycles on and off every few seconds, it is short-cycling. This is an indication that the pressure switch may be broken.
Push the tire-pressure gauge onto the valve on top of the pressure tank. This is the large (usually blue) tank attached to the plumbing system. A typical pressure tank should have about 30 PSI of pressure inside it. If the tank's pressure is considerably higher, the tank may be causing the problem.
Push the center needle on the valve on top of the pressure tank for one second, using a screwdriver. If water comes out of the valve, the bladder inside the tank has failed and the pressure tank needs replacing.
Go to the faucet and watch the flow of water. If the flow varies and the pump turns on and off erratically, it is most likely a broken pressure switch.