Replacing a Wall Switch

Wall-mounted toggle switches usually warn you before they fail completely. If there is a brief delay before the lamp lights, or if the lamp flickers a bit when it is turned on, the switch probably needs to be replaced. Buy the correct type of replacement switch and follow safe electrical practices. The job itself is easy.

Switches that are used the most usually fail first. When a frequently used switch shows signs of failing, other much used switches of the same age will probably also need replacement soon. It may save time and trouble to purchase and install several switches at once, rather than wait for the unexpected failure. Be aware though, that sometimes the fixture controlled by the switch is faulty, not the switch; a loose wire connection makes a good switch appear faulty.

When switches need to be replaced, be sure that the new switch is the same type as the old. If in doubt, the number, color and location of the terminals are good clues. The most common types of wall switches include the following:

Single pole is the simplest and most common type of switch used in home wiring. This switch completes or interrupts the hot-wire circuit; it has two brass terminals plus a green ground terminal and connects only to the black “hot” wires.

Three way is a type of switch that permits the control of lights or outlets from two locations. This switch allows a conductor connected to the center (or common) terminal to be joined to either of two wires. The switch has three terminals but only two switch positions. Current can flow through the switch in both positions. One position provides straight through connections and the other position provides crossover connections; since an electrical connection always exists, the switch is never truly “off.”

Four way is a special type of switch used to control lights or outlets from three or more locations. This switch has four terminals. Like the three way switch, current can flow in both switch positions so the switch is never really off.

Whatever type of switch you are replacing the procedure is basically the same; however, when replacing a three or four way switch, be sure to test all combinations of switch positions to be sure the current is off before you begin to work.

Turn off power to the circuit at main service panel. Remove cover plate. Test switch in both positions to ensure the circuit is dead, using a voltage tester you are sure is operational.

Once you are certain the circuit is dead, carefully remove the switch. Remove the wires, noting the location and color of the terminal to which each was attached.

To test a single pole switch with a continuity tester, connect the alligator clip to one brass terminal; touch the probe to the other. If the switch is good, tester will light for “on” but not for “off.”

Move clip to the metal mounting bracket or green terminal, if one is present. Touch probe to each brass terminal in turn and flip the switch on and off. The tester should not light in any position.

Install the new switch: insert wires into the same holes or wrap around the same terminals as in the old switch. Connect the ground wire (generally copper, if present) to the green terminal.

Tuck the wires securely inside the wall box and remount the switch. Turn on the power and test the switch before replacing the cover plate.

Push in connections. To disconnect this kind of switch, press a small screwdriver in the slot next to the hole where the wire enters, then pull the wire out.

Each switch in a circuit must be grounded to maintain the effectiveness of the grounding system built into your house wiring. To ground a switch, in a box wired with plastic sheathed cable, run a green jumper wire from the wire cap to the green grounding terminal.