Follow these steps to find which switch is bad. How to troubleshoot a faulty wall switch.
Understanding Three Way Electrical Switches
Can a 3 way switch go bad. One of the wires in the two three way switches is always hot assuming the circuit breaker is on. Locate a bad 3 way switch. Occasionally changing a light bulb may not be enough to restore illumination. A wall switch is a mechanical device with moving parts that gets thousands of uses over the course of its lifespan so its no surprise that switches eventually wear out and go bad. If the breaker is okay then the light switch is the next likely suspect. Sometimes one of the switches has become defective.
Toggle each switch until the light come on. The steps i am going to describe may not be the most time efficient way to troubleshoot a 3 way circuit. Be sure the wires are not touching anything and the bare copper ends are sticking out of the boxes and not touching anything. Usually when a 3 way switch fails lights can be toggled on and off at one switch but not the other. It turns out that none of the neutral wires were hooked up to the switches or the receptacles for that matter. The following method will address both problems at once.
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. The first sign of trouble is when the switch begins to behave in a fashion that is abnormal in any way. Disconnect all the wires from both switches. Modern dimmer switches can save energy and light bulbs but they are damaged more easily than the auto transformers and rheostats that had been used to dim lights before spiras invention. Start by turning off the power to the switch circuit at the circuit breaker. When i first investigated the switches on my own i assumed that this was normal for a 3 way switch in the same way that there is no neutral wire on a dimmer switch.
If one of the two 3 way switches toggles the lights on and off the other 3 way switch has probably failed. Sometimes a 3 way circuit doesnt work because someone tried to replace a defective switch and did not properly connect the wires. Dimmer switches have come a long way since 1961 when joel spira invented the first electronic dimmer switch. Wiring a 3 way light switch can be a difficult process particularly for diyers who are attempting the process with little to no electrical knowledge. The electric wiring could have a short the breaker may have tripped or the light switch may be bad. The moving parts of a standard light switch are enclosed inside plastic casing so when the switch goes bad your only option is to replace it.