Most wall switches in your home control light fixtures, but they can also control wall outlets (receptacles) or hard-wired appliances, such as a garbage disposal. Because these switches get frequent use (turning a light fixture on and off several times a day, for example), it's very common for them to wear out. But mechanical failure of the switch itself is not always the reason a light fixture doesn't work. A switch is only one component in a complex electrical circuit that begins at the circuit breaker panel, runs through electrical wiring in the walls to the light switch, then through additional wires to a light fixture, outlet, or appliance. When a light switch appears to be "bad," the problem can actually lie anywhere along the circuit, from circuit breaker to light fixture.
Troubleshooting a switch, then, is at least partly about troubleshooting the entire circuit to determine where the problem really lies. If your troubleshooting rules out other possibilities, then replacing the light switch is the final step.
When to Troubleshoot a Wall Switch
Whenever a wall switch no longer properly operates the light fixture, outlet, or appliance it's supposed to control, then it's time to undertake these simple steps to determine where the problem lies. Just remember that your investigation may turn up problems that have nothing to do with the switch.
Before Getting Started
Wall switches come in many styles, but aside from the aesthetic differences between simple toggle-type switches, button switches, slide-lever switches, and dimmer switches, there is a more basic engineering difference. There are single pole switches controlling things from a single location, three-way switches controlling lights or outlets from two locations; and for larger homes or complicated situations, a four-way switch may be used to control lighting or outlets from three or more locations. If your troubleshooting determines that there's an actual mechanical problem with the switch, then it's important to know what kind of switch you have before you purchase and install a replacement.
Equipment / Tools
- Non-contact circuit tester
- Continuity tester
- Wire connectors (if needed)
- New wall switch (if needed)
Inspect the Switch
Sometimes, a damaged or faulty switch will be immediately evident. If the switch's toggle lever or slide mechanism is loose or fails to operate correctly, then it's very likely the mechanical parts within the switch are simply worn out. Similarly, if the switch makes a buzzing sound, is warm to the touch, or shows any signs of scorching or melting, then it's almost certain the switch is faulty and needs to be replaced immediately.
A switch making audible buzzing signs or that is warm to the touch should be attended to immediately by shutting off the circuit breaker. Such a switch could pose a fire hazard and must be replaced as soon as possible.
Check Light Bulb or Outlet
If there's no obvious damage or problem with the switch, then rule out the easy things first: Make sure the light fixture has bulbs that aren't burned out, or that the lamp or appliance that's plugged into a switch-controlled outlet is working correctly. There's no sense spending time replacing a wall switch if the problem is just a burned-out light bulb.
Check the Circuit Breaker; Shut Off Power
A switch circuit that doesn't operate correctly may simply have a tripped breaker or blown fuse. Head to the electrical service panel and locate the breaker or fuse. If the breaker is tripped, reset it; or if the fuse is blown, replace it with an exact duplicate.
If resetting the breaker or replacing the fuse doesn't solve the problem, then your next steps will involve inspecting the wire connections and switch more closely. But before doing this, turn off the power to the circuit by switching the breaker off or removing the fuse.
Remove the Coverplate, Test for Power
Carefully unscrew the wall cover plate and remove it so that you can inspect the switch. Use a non-contact neon circuit tester to make sure the wires connected to the switch are not carrying live current. When probe is passed near the wires or switch screw terminals, it will light up if there is live current present. Never touch any wires until you verify that there is no current present.
Inspect the Wire Connections
In many cases, a switch will fail to operate correctly because wire connections—either circuit splices inside the electrical box, or wires connected to the switch itself—have become loose, preventing the circuit current from following its designated path.
Use a flashlight to peer into the electrical box and check the quality of the wire connections. To do this, it may be necessary to loosen the mounting screws on the switch and pull it from the electrical box.
If you discover bad wire connections, simply reconnecting them to the switch may solve your problem. If you notice loose circuit splices inside the box, use wire connectors to secure them.
Once loose wire connections are fixed, you can tuck the switch back in the electrical box, replace the cover plate, turn the circuit back on, and test to see if the switch works properly. If the problem persists, then turn off the circuit power again, and prepare to remove and test the switch itself (next step).
Remove the Switch
If your problem continues after the preliminary steps, then remove the switch from the electrical box (only after verifying again that the power is off), then disconnect the switch from its circuit wires. Usually, this is a simple matter of loosening the screws to which the wires are attached. Some switches may be secured to circuit wires with push-fit connections; with these, you will need to insert a small nail or screwdriver into release slots to disconnect the wires.
Test for Continuity
Use a battery-operated continuity tester to test the switch's mechanism. This is an easy test that involves holding the tester's probes to the screw terminals and flipping the switch's lever back and form. A small diode bulb lights up when the switch's mechanism successfully completes the pathway between the tester's probes. So if the test does not show continuity, it means the switch is faulty.
If the switch proves to be faulty, then installing a new wall switch is an easy project.