Nothing is more frustrating than trying to figure out why a 3 way or 4 way light switch system doesn't work. Years ago I got a severe brain cramp one day trying to hook up two switches. After I consulted some books, it became crystal clear how to do it. Ever since that day, I have memorized the wiring diagram to successfully hook up 3 & 4 way switches.

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Multiple Possibilities

The electrical wiring in your house can be installed in several ways. This can cause problems when trying to diagnose a wiring problem with 3 way or 4 way switches. If you decide to tackle this easy problem, it will help you immensely if you buy a continuity tester. This is a simple battery powered device that tells you when a circuit is complete.

Continuity testers are often electronic devices that have a needle gauge or a digital readout. There are always two wires that lead from the tester with metal tips. If you touch the wires together the needle should jump to the end. This shows that the current from the battery is flowing from one wire through the other wire to the gauge. Here is why we need this great tool.

If you goof up the wiring of 3 way or 4 way switches, you will need to determine which wires go where. There are basically two types of wires we are concerned with: the common wires and the travelers. The continuity tester allows us to figure out which wire is which.

There are only two common wires in each set of switches. One leaves the final switch and heads to the light. The other one enters the first switch and goes back to the electric panel. This is the line wire which provides the power to the lighting circuit.

The traveler wires are the ones that interconnect between the terminals on the switches. If disconnected from the switches, these wires would never hurt you. They do not connect directly to any 'hot' power source.

Using the Tester

To see how the tester works, find two pieces of electrical wire - each about 10 feet long. If this is single strand wire it will work just fine. Strip the insulation off each end of each wire approximately one half inch. Imagine for a moment that one of the wires is a wire that would be hidden behind a wall or ceiling that travels between two switch boxes. The other wire is one you need to drag with you during a test. (In reality, this test wire has to be long enough to reach between the two switches we are working with).

Take one end of each wire and connect them. Now you have one long wire. Touch one end to the continuity tester lead and the other end to the other lead. The tester needle should move. Are you starting to see what we will do? Yes, I thought you would. You are going to figure out which wires in each switch location travel between the two switch boxes. These are the travelers! The other wires are the commons.

4 Way Switch Problems

Four way switches must be placed in between two three way switches. You could, if you wanted to, control a light from 20 different switches! Eighteen of them would be four way switches and only two would be three way switches. I have personally installed a system where a light was controlled by six switches. It was a breeze!

What you must remember is where exactly each set of traveler wires connects. A set that is going to the next switch always connects at the top two terminals or bottom two of a four way switch. Do not attach two wires of the same set on the two screws on the side of a four way switch. Do this and you will be forever scratching your head!

New Installations

Trouble free wiring can be achieved if you are going to do a new house or add some switches in a remodeling job. The trick is simply to feed the first switch box with a wire from your electric panel. This wire contains a hot, neutral and ground wire. You then extend a wire to the next switch box that contains an extra wire. This type of wire is called three wire (three insulated wires - black, red and white). This extra wire (red) becomes one of the necessary traveler wires!

If you have a four way switch(s) involved, you simply continue to extend this same three wire in between each of the four way switch boxes. The last piece of three way wire goes from the last four way switch to the final three way switch.

Please be sure to turn the power off when you are wiring. It is foolhardy to work with 'hot' wires. Just ask my wife. I was showing off one day and ruined her new countertop with a shower of molten copper!

How to Wire a 4 Way Switch Video