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How To Troubleshoot 3-Way Switches?

A 3-way switch enables controlling wall switches from different locations. Setting up a 3-way switch is slightly more complicated than the conventional single-pole switch. In order to troubleshoot a 3-way switch, you have to understand the working on 3-way system as well as diagrams and colors. Besides, you should be aware of the variations in 3-way switch and here are all the details you need for 3-way switch troubleshooting.

How 3-Way Switch Works?

A standard switch has two terminals and a grounding terminal. On a 3-way switch comes with an additional terminal called the common terminal. You can identify the common terminal easily as it comes with a darker shade. The common terminal is responsible for moving current from power source or from one switch into the light fixture.

The other two terminals connect the wires between the switches of the 3-way system. These are called traveler terminals and traveling wires, respectively. These traveling wires come in red and black insulation for instant identification. These terminals can interrupt the circuit flow to turn off the light.

3-Way Switch Diagram

In a 3-way switch, you will be finding wires which arise from the power source until the light. There are hot wire and neutral wire entering from the left. The neutral wire is not concerned with switching and hence, whether the circuit will turn on the light or not depends on the hot wire.

As you can see in the second diagram, there is no way for the traveler wires to get through. But when there is the flipping of either switch, the hotness can get through. Accordingly, the lights are turned on and off.

3-Way Switch Diagram

Wire Colors in 3-Way System

It is important that colors have to be coded appropriately to prevent miswiring. In many cases, coding is done by the manufacturers.

  • The hot end of the hot wire has to be in red or black.
  • The traveler pair could be black+white or black+red or red+white.
  • The hot wire of the common terminal belonging to hot-end switch should be black/red/white.
  • The leg wire of the common terminal belonging to leg-end switch should be black/red.
  • The neutral wires are white and the bare or green color wires are grounding wires.

In many instances, people also tend to use white or red common terminals. The common terminal’s light leg wire can be black and in most cases, it can also be red.

The traveler pair has one cable which is either in white or black. There can be instances of red and white or black and red. It has to be noted that the white wires in the switch box are neutral you need to connect any green wires or bare wires on the ground. When there is an additional green screw, you will have to run the bare piece from the ground.

Standard 3-Way Switch Arrangement

3-way systems have a scheme theme of — S === S — O

Here ‘S’ stands for switches and the letter ‘O’ represents light. Also, the lines are the wires that provide switchable or constant hotness. In the above arrangement, there are no neutrals highlighted as they are not involved during switch operation. However, it has to be noted that neutrals can come in different ways. The arrangement also does not show cables or boxes or additional lights.

3-Way Switch Variations

We have already discussed the basic scheme of a three-way switch arrangement. Again it has to be noted that it can come in different variations according to the switch-related wires through boxes. Even the wire colors can be in different codes. Here are some common 3-way switch variations you should be aware of.

  • In a common 3-way switch, the hot comes at one switch box. The hot then is connected to another switch or the common switch. The travelers between the switches tend to give up the hotness which is called a leg. The leg can be from the nearest electrical switch or the light.
  • Another variation is that a three-way switch traveler placed in the light box. In this case, the travelers can switch from one end to another through the light box.
  • Focusing on the schematic of 3-way switches, there can be hot from the system which comes out from the light box. However, it becomes functional only when the switch is connected. In doing so, the other switch will send the travelers back to the same cable by bringing hotness down.

Here are the factors that determine the variations of a 3-way switch.

  • House cables can have two or more insulated conductors.
  • The circuit direction is coming to the area.
  • Restrictions regarding cabling.
  • The physical relationship between the lights and switches.
  • The preferred usage of the electrician.
  • Electrical boxes capacity to hold switches, lights, and wires.

3 Way Switch Troubleshooting –

There are many reasons that could lead to the malfunctioning of a 3-way switch.

  • It can happen when one of the switches can fail.
  • Another reason can be due to inappropriate installation when there are only two terminals. When there is a replacement of the toggle handle style switch, there is a likelihood of having malfunctioning. Thankfully it can be prevented by attaching screws of the same colors.
  • One of the major causes of malfunctioning can be when the connection of the wire becomes loose. You can easily troubleshoot it without disconnecting anything. All you have to do is to use a neon tester and check if the switch is turned on. When the tester is hot, it indicates that it is the hot end. You can move on to the next switch to check the hotness.

Things to Keep in Mind While Troubleshooting a 3-way Switch:

  • The two travelers must be at the same cable with each other.
  • The multiple switch system which is not hot must be disconnected from their wires.
  • Switch screws pairs that are in the same color have to be identified backward.

Steps for testing 3-way switch:

  • Shut down the power supply to the switches. Use a tester to ensure there is no power.
  • Remove the switches to get access to the switch terminals.
  • Use a continuity tester to check common and traveler terminals in both switches.
  • Normally, there should be a connection between the common and any one of the traveler terminals.
  • When you toggle the switch, there should be a connection between the common and the other traveler terminal.
  • If the switch fails, there will be no connection between the common terminal and the traveler terminals in either of the above-mentioned scenarios.


Troubleshooting any switch is dangerous unless you have proper knowledge about its configuration as well as the coloring of the wires. Always take all the proper precautions so that there is no mishap while troubleshooting. One wrong move can cause fire and bodily injury as well as home damage. Therefore, take your time to understand the setup if the 3-way switch is already installed and thereafter, go for the diagnosis as per the problem.

One Response

  1. 3 switch lighting for stairs/landing has suddenly come on and only goes partially off or on as if lighting is dimmed. No dimmer switch in circuit. Lights will not totally go off. Either dimmed or normal lighting from either of the three switches in circuit.

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