When you flip a switch in your home and nothing happens, you have to start thinking about what could be wrong. Testing the switch is an option, but should be done after checking the most obvious possible problems first. Those might be a burned out bulb, a tripped circuit breaker, or even a fuse that may have blown. But when one of these isn’t the solution, then it is very likely that the trouble stems in the switch itself or the wiring associated with the switch. To narrow down your search and identify that the switch is the culprit, you can perform an out-of-the-circuit test or an in-circuit test to examine the switch.
Out-of-the-circuit switch testing requires the use of a continuity or multi-meter tester. You’ll need to test the switch out of the circuit, so you will need to turn the circuit off before proceeding with this test. Simply turn off the power, remove the switch carefully, test the wires with a voltage tester, multimeter, or a non-contact tester to see if the power is indeed off before working on the switch. Next, remove the wire from the switch by loosening the wires and removing them. Now that the switch is removed, touch one of the two test leads to one switch terminal and the other test lead to the other terminal. On the continuity tester, nothing needs to be set, but on the multimeter, you’ll need to set the dial to ohms read resistance or the continuity setting that will show if the switch is completing a circuit when switched. If the switch is flipped, the light on the tester will light, beep or the ohm value will change from nothing to something, depending on the type of tester that you are using.
In-circuit testing requires the use of a voltage meter or multi-meter tester. Again for safety reasons, turn off the circuit before removing the switch from the box. This will aid in the testing processing and help avoid the possibility of shorting the test leads against the side of the junction box. You will need to locate the white neutral wire or ground wire where one of the leads will be placed. Remember that the multi-meter will need to be set to the 120-volt setting before using this tester. Now, turn on the circuit and use the tester to check each terminal of the switch with one lead while touching the other lead to the neutral or ground wire. In one switch position, one terminal should be hot and other not. But in the other position, flip the switch, both terminals should be hot. If not, then the switch is likely bad and needs to be replaced. However, if everything checks out, it could indicate that there is a wiring problem between the switch and the light or a loose connection, possibly a bad splice.
Obviously, single-pole switches make our lives much easier and have saved many a toe from being stubbed from the olden days of walking across a dark room to reach a pull-chain fixture located in the center of the room or a desk lamp across the room. With a few simple electrical tools, you too can keep your lights glowing and find problems with single-pole switches. With these simple steps, now you will be armed with the know-how of testing switches.