How To Install a New Switch

Man installing switch
Of all the different home improvement projects that homeowners have to deal with in the normal maintenance or remodeling of their homes, the one area that seems to make people the most skittish in doing themselves is working on their electricity. A few electrical projects around the home are fairly easy and with a little instruction, are as safe as screwing in a light bulb.

There are a few reasons for replacing a switch in your home: The switch no longer works or is damaged, changing the color or style of the switch, or swapping an on/off switch with a dimmer. Whatever the reason, you should be aware of the different types of switches so you aren't overwhelmed when you are at the hardware store buying a new one.

Different styles:

  • Toggle switch - The basic switch that most everyone is familiar with, named because the switch "toggles" up and down.
  • Rocker switch - This switch has a pad that is high on the top or the bottom (depending on whether it is on or off) and low in the middle and operates similar to a teeter-totter. It is more expensive than a toggle switch and is part of the Decora line of electrical devices that has matching outlets which are rectangular instead of the traditional look with two round outlets.


  • Toggle - Looks identical as above but instead of the switch clicking on, you can gradually lift the toggle adjusting how bright the light goes on.
  • Rotary - This has a round dial that you spin to adjust the brightness.
  • Slide - Usually a disc-shaped button that slides up and down.
  • Touch - A touch pad that operates with slight pressure.

The switches listed above can have different functions and are labeled with one of the following:

  • Single pole - One switch operates one light or set of lights. It has two screws on its side where the wires connect to it. (This switch is the most common.)
  • 3-way switch - This switch is used when you have two switches that operate one light or set of lights. These are located in your home where you have two entrances to a room so you can turn the same light(s) on/off from either doorway. It has three screws on its side where the wires connect: one black and two brass-colored. (Most homes have at least one set of these - found usually in the living room, kitchen or at the top and bottom of a staircase.)
  • 4-way switch - Same as above with three switches operating one light or set of lights. It has four screws: usually two black and two brass-colored. When there are three switches operating a light(s), two of the switches are three-ways and one is a four-way. (These switches are not very common.)

Note: All of these switches (unless your old one is really old) will have a green screw on one end called the grounding screw. If your home has its wiring running through metal pipe (called electrical metal tubing or EMT), you can ignore this screw as the EMT acts as the ground. You should be able to tell by looking at your electric in an unfinished area of the house and your old switch will have nothing connected to this screw. If your house is wired with Romex ® (a flat vinyl-coated cable that has several wires in it, like a large extension cord), then you should find a wire connected to the green screw on your old switch and should reconnect this wire to the green screw on the new switch. This wire only gets electrified if you have a dangerous short, when it will trip the circuit breaker or blow the fuse, killing power to the faulty circuit. It is an important safety feature, but doesn't get used in the normal operation of the switch.

Installing the switch

  1. Turn off the power to the circuit that the switch is on by how to wire a rocker switchflipping off the circuit breaker or taking out the fuse, depending on which type of load center you have. If for some reason you can't tell which circuit the switch is on, turn off the main breaker at the top of the circuit panel or pull out the main fuse (the big one at the top that has two cylindrical fuses) so that the power is out to the whole house. Check to make sure everything is off.
  2. Unscrew the switch plate and remove.
  3. Unscrew the two screws holding the switch to the electric box. Gently pull the switch toward you out of the box a little ways so you can work on it after screws are out.
  4. Take the wires off the old switch. Unscrew the screws holding down the wires and pull them off with pliers. Sometimes the wire will be pushed into a hole in the back of the switch (a quick connect feature on most switches that professionals usually don't utilize because they aren't as secure as using the screws). In this case, you will have to push a very small slot screwdriver into the slot directly next to the wire while pulling out the wire with pliers. If you don't have a small flat tool to use, you can cut the wires off right at the switch to keep them as long as possible, then use a wire stripper or knife to strip off approximately 3/4" of the insulation off the end of the wires to prepare them for the new switch. Be careful not to nick the copper while stripping. If you are putting in a three-way or four-way, it is a good idea before taking the wires off the old switch to hold the new switch up to the old one, noting the positions of the wires.
  5. Connect the wires to the new switch.

    • If you're replacing a single pole switch that has only two wires, not counting the ground wire to that green screw if your old one had one, this one is a no-brainer because it doesn't matter which screw the two wires go to. Just wrap one around each screw and torque down.
    • If you're replacing a three-way switch, match the wires the way the old one was wired. There are three connector screws: one black and two brass ones. It is a good bet that the wire going to the black screw will be black, and the two brass screws will have wires of another color (but these two will match). Red, blue, orange, purple and yellow are the most common colors for these wires. It doesn't matter which of the brass screws they go to, as long as the two same-colored wires are connected to the brass screws.
    • For a four-way switch, there are two screws of one color (sometimes marked "in") and two screws of another color (sometimes marked "out"). Make sure the two wires going to the two screws of the same color on the old switch get reconnected to same-colored screws on the new one.

  6. Push the wires and switch back into the box. Attach new switch to electric box with screws.
  7. Put switch plate back on.
  8. Turn back on the power.

Dimmer switches are slightly different only because of the fact that instead of having screws on the side to attach the wires to, there are wires (leads) already coming out the back. For a single pole, there will be two black wires. Connect one of them to one of the wires that was connected to the old switch and the other dimmer wire to the remaining wire from the old switch. Secure the wires by twisting them together with wire nuts that usually come in the dimmer packaging. Gently tug on one wire, then the other while holding onto the wire nut to make sure they are secure. It is a good idea to wrap some electrical tape around the wire nuts and wire so they don't loosen.

The three-way dimmer has one black wire and two same-colored wires coming out the back. Connect the old switch wires to the dimmer the same way as the three-way described above using wire nuts, connecting one of the dimmer's colored wires to one of the old switches colored pair, then the other two colored wires, and finally the two blacks. In some odd situations, you may have another color than black on your old switch, but there will always be a pair the same color and one wire of a different color. That different-colored wire would go to the black lead on the dimmer. You can only have one dimmer on a light; the other switch will only turn the lights on to the brightness the dimmer at the other location is set at.

There are no four-way dimmers. If you have three switches operating one light(s), and you want to be able to dim these lights, you will have to purchase a three-way dimmer and replace one of the two three-ways. If you pull one of the switches out of the electrical box and it is the four-way, put it back. The dimmer cannot go at this doorway. You will have to put the dimmer at one of the other two switch locations.

ROMEX is a registered trademark of Southwire Company.


Share this article!

Follow us!

Find more helpful articles: