Deep well or submersible water pumps reside under the water level of the subterranean water source. Many parts make the pump operate. For example, an electrical pressure switch turns the water pump on and off, and some submersible water pumps utilize a pump relay that adds an extra boost to the underwater electric motor. A single check valve sits on top of the pump housing, retaining water in the main plumbing pipe. Testing for a bad deep well pump involves inspecting those items and the well.
Verify that the water pump system receives electric power. Turn the circuit breaker on and off a couple of times to ensure it doesn't trip. If the electrical supply uses fuses, install new fuses.
Gain access to the top of the deep well. Remove the top cover according to its type of enclosure. Different types of deep wells have various methods that enclose the top of the wellhead.
Check for water in the well. Shine a flashlight down the well. If you see that water covers the submersible pump, the well has plenty of water. If you can see the pump housing, the well is dry and must recover.
Inspect the system's pressure switch. The switch is in close proximity to the pressure tank and is attached to the well pump plumbing pipe. Shut off electric power to the water system. Remove the gray plastic cover to the switch housing by turning the top screw in a counterclockwise direction with plumbing pliers. Lift the cover from the switch. Look at the electrical contacts that conduct electricity to the pump or pump relay. If the contacts are closed, open the spring-loaded discs. If the contacts are severely pitted or black, the pressure switch may be bad and in need of replacement. If the contacts are stuck open, try cycling them a few times. Apply electrical power.
Check the pump relay's capacitor if your system has a pump relay. Trace the wires from the well pump system's pressure switch. If they go to a gray box on a nearby wall, you have a pump relay. Shut off all electrical power. Open the gray box by removing the single screw at the bottom of the enclosure. You will see a cylindrical capacitor and a square relay. Inspect the capacitor for signs of leaking fluid or a swelled housing. If either condition is present, the capacitor is bad and needs to be replaced.
Inspect all wires and the screw terminals for the wire connections inside the pump relay. Tighten the screws with a screwdriver. If you find a loose wire, close the pump relay cover and apply power. If the pump still fails to operate, the pump may be the problem.
Connect an ohmmeter to ohmmeter leads. Ensure all electrical power is off to the pump system. Insert the red lead into the ohmmeter's connector marked "ohms." Place the black lead into the ohmmeter's "com" connector. Switch the front dial on the meter face to "X1 ohm." Touch the metal ends of the leads together. The display must read 0 (zero) ohms.
Examine the system's resistance with the ohmmeter. Find the wires that lead to the submersible water pump inside the deep well. Typically, the system has three wires: a red insulted wire, a black insulted wire and a yellow insulated wire. Touch the ohmmeter's red lead to the red wire and its black lead to the black wire. The ohmmeter display must read some form of resistance. If the display reads "inf" or infinite ohms, either the pump is bad or the wires inside the well are broken. If the meter displays resistance, remove the black lead from the black wire and touch it to the yellow wire. If the ohmmeter reads no resistance, the starting windings to the pump are bad or the wire is broken.