This Fix-It Guide tells how an electrical switch works, what often goes wrong, how to identify an electrical switch problem, and what parts and tools you will need to fix it. It gives instructions for how to test various switches as well as how to perform basic electrical switch replacement, three-way switch replacement, and dimmer switch replacement.
How Does an Electrical Switch Work?
An electrical switch is a device designed to break the flow of electric current. When turned on, a switch completes the electrical circuit and current flows to the light or other device the switch controls. When the switch is off, the electrical circuit is not complete, denying power to whatever the switch controls.
The most common household switch is a two-way (sometimes called a single-pole) switch, which is a toggle switch marked on and off. Other household switches include the three-way switch for controlling a light from two switches, and the dimmer switch for varying the amount of electricity that goes to the light or other apparatus.
What Can Go Wrong with an Electrical Switch?
Switches, by design are relatively simple, so typically either they work or they don’t. The other option is that they don’t work safely, meaning the electricity arcs or sparks in the switch–a potential fire hazard.
Most electrical switches wear out from use in 5 to 20 years, depending on quality and frequency of use. Additionally, wires can become loose and not make connection, caused by poor installation or other factors.
If you’re buying a new switch that will get lots of use, spend a little more and buy one that is labeled “commercial” or “spec-rated.” Internal parts are sturdier and will stand up to use longer–and more safely.
How Can I Identify an Electrical Switch Problem?
An electrical switch problem can have one or more of these common symptoms: The light fixture (or other device) doesn’t turn on even with a new bulb, the switch pops when you turn it on, the switch wiggles when you flick it. In each of these cases, switch replacement is required. Fortunately, switches are inexpensive and you can replace one without having to test it.
Only one electrical switch in a group of three-way switches can be a dimmer switch. The remaining switch must be a standard three-way.
What Do I Need for Electrical Switch Repair?
You can find replacement electrical switches at most hardware stores and home improvement centers. Specialized switches may require that you visit an electrical or lighting supply store. In addition, you may need some of these tools:
- Continuity tester or multimeter
- Wire stripper
- Electrician’s tape
- Masking tape
What Are the Steps to Electrical Switch Repair?
Test an electrical switch:
- Turn off power to the switch’s circuit at the electrical service panel. This requires identifying the correct circuit breaker and turning it off, or finding the appropriate fuse and unscrewing it from the panel.
- Remove the cover plate and use a tester to make sure power is off before proceeding.
- Disconnect the old switch by removing the top and bottom screws holding the switch to the electrical box that is mounted in the wall.
- Pull the switch toward you to expose the wires on the side and rear. If a wire is loose or broken, you’ve probably found the problem.
- Unscrew the terminal screws on the switch about 1/4 inch and remove the wires. Some switches, instead, have wires inserted into holes in the rear of the switch; if this is the case, insert a small thin screwdriver in the slot below the wire to release it.
- Use a continuity tester to test the switch. Clip one probe to each of the two terminals, then flip the switch on and off. The tester should light only when the switch is on. You also can use a multimeter set to resistance in ohms for this test. If the switch is faulty, replace it.
Replace a basic electrical switch:
- If any wires from the box are damaged, remove the damaged portion, making sure you have sufficient length to reach the terminal box.
- If necessary, use a wire stripper to remove insulation from the last 3/4 inch of the end of the wires.
- Use the strippers or pliers to bend the end of the wire in a semicircle so it can wrap around the terminal screw. If there are no terminal screws on the switch, insert the straight wires into the appropriate holes on the back of the switch.
- Attach the wires to the terminals and tighten them.
- Replace and screw the switch into the terminal box, making sure the switch is plumb–straight up and down.
- Replace the cover plate, restore power, and try the switch.
Replace a three-way electrical switch:
Follow the above steps for replacing a two-way or single-pole switch. The primary difference is the number of terminals; three-way switches have an additional or common terminal. Make sure you mark the terminal and wire locations as you remove the old switch and install the new switch in the same way.
Replace an electrical dimmer switch:
- Shut off power at the electrical service panel. Pull off the rotary knob of the switch with firm outward pressure. Underneath is a standard switch cover plate. Remove the cover plate. Remove the mounting screws and carefully pull out the switch body.
- A dimmer has wire leads instead of terminals. Remove the wire nuts and test for power by touching the probes of the tester to both wires, or to either wire and the metal box, or to one wire and the ground wire. If power is detected, shut off the correct circuit in the service panel.
- With probes of a continuity tester touching the terminal on each side, the tester should show continuity with the switch on and no continuity with the switch off. If you get different results, replace the switch.
- As needed, replace the switch by connecting the dimmer wires to the power wires with electrical nuts.
If three switches control a single light or group of lights, they are actually four-way switches. Count the number of switches and add one. Make sure you get the correct replacement switch type for the job.