Double switches in a room often use one switch to control a wall outlet and the other switch to control an overhead light or ceiling fan. The most common double light switch is a single pole switch. If no other switch in the room operates the same devices, it is a single pole. If there are other switches in the room operating the same devices, than you have a three-way switch. This is important to know when changing a defective double light switch, because you need to purchase the correct replacement.
Turn off the circuit breaker to the light switch and the components that it operates. This circuit breaker will most likely cut off power to the entire room. Remove the four screws that secure the switch cover plate to the wall with a flathead screwdriver and pull the plate off the wall.
Place one probe of a neon circuit tester on the bare copper wire and the other probe on a terminal screw on the side of the switch .If the neon light does not illuminate, move the probe on the terminal screw to the next terminal screw. If the neon light does not illuminate, the switch is safe to handle.
Remove the retaining screws that secure the individual switches to the junction box with the flathead screwdriver. Place small pieces of tape around each wire that connects to the individual switches and write the terminal location on each with a pencil.
Loosen the terminal screws on the sides of the switches with a Phillips-head screwdriver and remove the wires from the switches. Examine the wire ends for breaks or burns. Cut as little off the ends as necessary with a pair of wire strippers and remove 1/4 inch insulation off the wire ends. Bend the ends into small hooks with a pair of needle-nose pliers.
Hook the wires over the necks of the terminal screws on the new light switches, ensuring that you place the wires on the correct terminal according to the locations you wrote on the tape. Tighten each terminal screw with the Phillips-head screwdriver to secure the wires.
Secure the switches to the junction box with the retaining screws and position the switch faceplate over the switches and against the wall. Secure the face plate with the securing screws. Turn on the circuit breaker to power the switch.
Single pole switches have two terminals and a ground wire, while three-way switches have three terminals and a ground wire. You must replace the switch being removed with the same type of switch.