A 4-way switch allows you to turn on or off a light from multiple location, so you don’t have to be in the dark. The 4-way switch creates a way to have a switch at all entrances of a room or garage with 3 or more entrances or a long hallway with many rooms off of it.
If you have a basic understanding of a 3-way switch, then adding a 4-way switch in between is fairly simple to understand also.
Check out our article on understanding a 3-way switch if you need help with that.
The 4-way switch basically breaks the one traveler an sends current down the opposite traveler causing a current flow change in the power to the 3-way switches.
This great video explains how it all works.
You now understand how a 4-way switch works, but sometimes the person before you didn’t use standard wiring practices and you may see wire colors that make it hard to figure out. If you are just replacing a switch it is best to draw a diagram and mark the wires so you can put them back the way they come off the old switch. Although it is good to note that some manufactures use a different screw pattern for their switches, go figure.