Usually when a 3-way switch fails, lights can be toggled on and off at one switch, but not the other. If one of the two 3-way switches toggles the light(s) on and off, the other 3-way switch has probably failed. Follow these steps to find which switch is bad. Toggle each switch until the light come on.

Can you wire a three-way switch wrong?

One of the most common problems that homeowners face when tackling this project themselves, is improper wiring, which happens when the circuit wires are connected to the wrong screw terminals. Its incredibly easy to accidentally confuse the wiring of a three-way switch when youre performing a replacement at home.