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Electrical: Replacing a Wall Switch

Electrical testerWhile most wall switches may last for decades, they do sometimes fail. Replacement isn’t dangerous if you follow a few simple guidelines, and can be accomplished in minutes. First, turn off the circuit breaker that controls power to the switch. Once the breaker is off, I use a simple tester to confirm that the circuit is no longer hot. If you have difficulty determining whether or not the power is off, turn off the main circuit breaker; but have a flashlight handy.

Remove the plastic switch cover, and then remove the two screws holding the switch in the electrical box. If the switch is a standard wall switch, controlling one light or device from only one location, it will have either two or three wires. Some older homes with 2 wire circuits lack the extra ground or bond wire that was added many years ago as a safety precaution to avoid electrical shock. Caution: Switches connected to two white wires can create an electrical hazard. Call an electrician if you discover this type connection.

In a typical three wire system, the switch will have a black, a white, and a bare copper wire OR two black wires and a copper wire. (Loosen the screws holding the three wires and dispose of the old switch. If you find 4 wires on the switch, it’s probably a 3-way, a switch that works in conjunction with another to control a circuit. If that is the case, you may need to take the switch with you to your home center or hardware store for replacement. (Refer to the section: Replacing a 3-Way Switch) If the wires are not secured by screws, but instead enter holes in the back of the switch, there are two options. You may insert a small screwdriver or ice pick into the slot adjacent to the hole or just cut the wires off where they enter the switch. If there is sufficient wire, I normally cut them off.

Newer switches will offer the same option; you can strip the insulation to allow you to insert the wire into the hole in the new switch or you can use the screws on the side. The screws offer a more secure connection, and I like that method best, especially if the light or device controlled consumes significant power. It helps avoid future problems. (Many times I have removed non-functioning switches only to discover that the electrician had used the rear holes and the wire had worked its way loose over time.)

The bare copper wire should be connected to the green “ground” screw. The other wires can go to either terminal, since on a switch you are merely breaking the circuit. If, however, your switch works in conjunction with one or more switches and has red, black, and white wires, you must re-connect to the same terminals as they were located on the old switch.

Caution: If your wiring appears to be aluminum instead of copper, it’s best to call an electrician to complete the job and to test for other problems. Some older homes were built with aluminum wiring which was later discovered to pose a potential fire hazard. If you think your home has aluminum wiring, call an electrician for an inspection.


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