Most of the wall switches in your home are single-pole switches that control a light fixture or outlet from a single wall location. Because they get so much use, wall switches eventually wear out and need replacement. If a wall switch has lost its snap or feels loose, if you notice buzzing or crackling when you operate it, or if it fails to control the light fixture, it's time to replace the switch.
Light Switch Wiring
Light switches operate by providing an operational break in the hot circuit wire leading to a light fixture or other device. Flipping the switch's lever opens and closes the hot wire circuit leading to the light fixture, allowing you to turn it on and off at will. There is no neutral wire connection in most light switches, which makes replacement fairly easy—it's a simple matter of disconnecting two hot wires from the old switch and reconnecting them to a new switch. For a basic single-pole switch, you don't even need to pay attention to which hot wire gets attached to which screw terminal—they are interchangeable.
That said, any electrical repair has the potential for complications. This is especially likely when you are dealing with old wiring, where the color-coding of wires may be missing, or where you face a bewildering array of wires passing through the electrical box. But the key is to simply pay attention to which wires are attached to the switch, and make sure they are attached in the same way to the new switch.
One very common complicating factor involves how (and if) the switch is grounded. For many years, it was common for wall switches to be installed without any grounding wire connection at all. If circuit ground wires were present in the electrical box, they were simply joined together to pass through the box. But some time ago, the electrical code mandated that wall switches needed to have a grounding connection. As a result, all new switches you purchase will have a green grounding screw on the mounting strap. When replacing an old switch, you will need to connect the new switch to the circuit ground wires, even if your old switch had no such grounding connection.
Before You Begin
Turn off the power by switching off the circuit breaker that controls the circuit feeding the switch. In older systems that have fuse panels rather than circuit breakers, the power is turned off by unscrewing the fuse that protects the circuit you are working on.
Return to the wall switch and flip the switch to confirm that power has been turned off. If not, return to the panel to locate and turn off the correct circuit breaker.
Equipment / Tools
- Non-contact circuit tester
- Wire cutters (if needed)
- Wire stripper (if needed)
- Needlenose pliers
- Single-pole wall switch
- Electrical tape (if needed)
- Grounding pigtail (if needed)
- UL-rated wire connector (if needed)
Remove the Cover Plate and Test for Power
Remove the wall switch's cover plate by removing the mounting screws. Test for power using a non-contact circuit tester. Insert the probe of the tester into the box alongside the screw terminals on the switch. The tester will light up or make a sound if there is live current in the box.
Extract the Switch
After verifying that the power is off, remove the strap mounting screws that hold the switch to the box, then carefully extract the switch by pulling outward on the straps. Be careful to avoid stressing the wires. Old wires may be brittle and the insulation can crack if you're not careful.
Examine the Wires
Take note of how the wires are connected to the switch. In newer wiring made with NM cable, the wires will have black insulation, and likely will be attached to brass or copper-colored screw terminals along one side or on opposite sides of the switch body.
In some configurations (known as a switch loop), the switch may be connected to a black and a white wire that has been marked with black tape to indicate that it serves as a hot wire.
There may also be a green grounding screw attached to bare copper circuit grounding wires, but this is not always the case.
With an older switch, the wires may have a rubber or cloth insulation without any color coding. Modern practice is to label these wires with black tape to identify them as hot wires. If they are not color-coded, it is a good idea to do this now.
If your wall switch has three or four insulated wires connected to it rather than two, you are not looking at a standard single-pole switch, but rather a 3-way or 4-way switch. These switches are used to control a light fixture from two or more wall locations. You can still replace this switch, but you will need to make sure you install the proper type of switch, and you will need to be very careful to connect the wires in exactly the same way they are connected to the old switch.
Disconnect and Remove the Switch
Extract the switch far enough out of the box that you can reach the screw terminals with a screwdriver, then disconnect the circuit wires. Examine the wire loop at the end of each wire. If it is nicked or damaged, snip off the damaged portion of the wire, then strip about 3/4 inch of insulation to expose new copper wire.
If the switch has a grounding screw attached to circuit ground wires, also unscrew this connection.
Attach a Grounding Pigtail (If Needed)
If your old switch had no grounding connection, you will need to attach a grounding pigtail to the circuit grounding wires. The other end of the pigtail will be connected to the grounding terminal on the switch.
Grounding pigtails are available as short green-insulated wires designed for this purpose, or you can create your own grounding pigtail by using a short length of bare copper or green insulated wire. Connect one end of this grounding pigtail to the grounding circuit wires in the box. Usually, this involves removing the wire nut that is joining the circuit grounding wires, then bundling the end of the new pigtail to those wires, and screwing the wire nut back on again.
Connect the New Switch
Connecting the new switch is a matter of making three wire connections: the grounding pigtail, and two hot wire connections. First, form a clockwise, C-shaped loop at the end of each wire.
Next, attach the free end of the grounding pigtail to the green grounding screw on the strap of the switch. Loop the wire around the shaft of the screw, then tighten it down firmly.
Then, attach the two hot wires to the screw terminals on the side of the switch body. Tighten the screws fully and tug on them to make sure they are secure.
In older homes that have metal boxes, it can be advantageous to wrap the newly connected switch with electrical tape to cover the connection points and wires. This helps avoid shorting out the circuit, something that can occasionally happen with old wires and metal boxes.
Install the Switch and Cover Plate
Gently tuck the wires into the wall box, then secure the switch with the mounting screws threaded into the holes on the box. Make sure the switch is positioned right-side-up so that the ON/OFF marking reads correctly. Carefully align the switch so it is vertical in the box, then attach the cover plate.
Turn on the power to the circuit at the circuit breaker box, then test the operation of the switch.
When to Call a Professional
Replacing a wall switch ranks among the easier of home electrical repairs, but any time you are working with electricity, there is the potential for shock. Replacing a light switch is a project best done by a DIYer with experience in electrical repairs and some understanding of circuits. If this doesn't describe you, then you may be better off calling an electrician to do this work. And don't be afraid to call a pro if you begin the repair but find that circumstances aren't what you expected.