When a 240-volt switch no longer works, you will need to replace it with a new switch. However, a 240-volt switch has two more wires than a standard 120-volt electrical switch, so to wire a new 240-volt switch, you will have to run two additional wires from the circuit panel. You will need to wire a 240-volt switch using five electrical wires, but the job is nearly identical to wiring a standard 120-volt switch.
Go to your home's circuit panel and turn off the circuit for the room with the outlet you need to wire. If you cannot locate the circuit, turn off the main switch.
Take the outlet cover off by removing the single screw with the screwdriver. Remove the screws that are securing the existing switch to the electrical box.
Disconnect the wires from the screw terminals on the switch. You will have five wires that are hanging in the electrical box. Two wires are hot, two wires are for the load and the last wire is the ground.
Attach the green wire to the ground screw on the 240-volt switch. Attach the two hot wires to the red and black screw terminals. Attach the two load wires to the blue and yellow screw terminals.
Verify that the wires are connected to the proper screw terminals, then tighten the screws to secure the switch to the electrical box.
Turn the circuit or power on at the circuit panel.
Press the switch to turn on the load. You should hear a "click" when the load comes on. Press the switch again to turn off the load.
Set the faceplate on the switch and tighten the screw.
Turn on the power and test the wires with a voltmeter to see which ones are hot. If the switch has wires already connected, you can use a wire cover to splice the wires together.