Four-way circuit turns on/off randomly

Question

My upstairs hallway lights are controlled by a four-way switch circuit. There are three switches to control two dome lights. One switch at the bottom of the stairs, one at the top and one at the end of the hallway.

When we moved in a year ago any switch would turn the lights on or off without issue. Recently the switches don't seem to work. Then randomly the lights will turn on. One time my wife noted that when she flipped a switch the lights flickered but remained off. I think it is a loose connection of a bad switch, but I am not sure how I diagnose the root of the problem.

Answer 1

It's either a loose connection, a bad switch, or a poltergeist.

• Turn power off to the circuit.
• Verify power is off.
• Remove the cover plate from each switch.
• Remove the screws holding the switches to the box (should be two, one top, one bottom).
• Pull the switches out a bit.
• Inspect the wiring and connections, looking for loose wires, charred/burnt/melted parts, and any other damage.
• Pull the lights down, and inspect the wiring there as well.

If you don't find anything, try replacing the switches. If there are 3 switches controlling the circuit, then you'll need two 3-way switches and one 4-way switch.

If you don't feel comfortable doing this type of work, contact a local licensed Electrician.

Answer 2

You will inevitably be taking some of these switches out. Do not look at physical positions of the terminals on switches. If you see wires on upper-left, upper-right and lower-left, that doesn't mean anything - discard that knowledge. It is useless. If you hook up the new switch that same way, anything could happen!

You need to learn the basics of 3-way and 4-way wiring, so you know what you're looking for.

Then - look at screw colors, and switch markings, to identify the correct wire groups. Mark the wires if you need to. Only then take them off the old switch.

You'll find lots of 3-way switch drawings on the Internet. But here's something you won't often see: a 3/4-way switch drawing that highlights the wires by function. Obviously, the colors you find in the box would be different.

Simple fact is, each of the two messengers is interchangeable. They might as well be the same color, and they often are in conduit with individual wires.

Notice that the diagram is vague and unclear about which physical positions those terminals are on the switch. That's because every switch is different, and you have to go by markings and screw colors.