Learn how to wire a 3-way switch system using our neat simple schematic and wiring diagrams (pdf included). Basically, you need to feed in power at the switch or at the light and set out one or multiple lights (2 lights, 3 lights, 4 lights or more) first, in the middle, or last in the configuration. This guide is for planning, installing, repairing, replacing, and troubleshooting both common (standard) and old-style (non-standard) 3-way light switch systems.
Table of Contents
About the 3-Way Switch System
A three-way switch system allows for controlling (putting on and off) a light fixture from two different locations. Each of the switches is positioned at either of the two locations from where the light fixture is to be controlled.
A three-way switch wiring system will enable you to conveniently turn on or off a light or set of lights from two different locations.
By correctly connecting two three-way switches together, toggling either switch turns a light on if it was initially off, or turns it off if it was initially on. A three-way switch system can be used to control a single light or a set of multiple lights (2, 3, 4, or more lights).
Common places where the two switches of a 3-way switch system may be installed to facilitate convenience in operating lights include:
- At either end of a long corridor or a staircase.
- At either door of two doors leading into and out of the same room.
- One at a bedroom door and the other close to the bed (bed switch).
The two switches may be wired in such a way that the switch toggles are in the same orientation for on, and opposite orientation for off. Alternatively, they may also be wired such that the switch toggles are in opposite orientations for on, and the same orientation for off.
Tip: It is important to note that, although three-way switches are commonly used to control lights, they can also be used to control other loads (e.g. socket outlets, fans, pumps, heaters, or other appliances) in a similar way.
Tools & Materials Required
The specific tools that you will need may slightly vary depending on the exact tasks entailed in your project. The tools you will require include the following (Read more about tools for electrical projects):
- Tape measure
- Fish tape
- 4-in-1 screwdriver
- Needle-nose pliers
- Utility knife
- Wire stripper/cutter
- Non-contact voltage tester
The material you will require may include the following:
- Black electrical tape
- 14-2 nm cables (or 12-2 nm cables)
- 14-3 nm cables (or 12-3 nm cables)
- Lights, their boxes and screws
- 3-way switches, their boxes and screws
- Wire nuts (twist-on wire nuts) or lever nuts (lever wire nuts)
The specific materials and quantities that you will need may vary depending on your choices and the requirements of your project. You can determine this by assessing your choices and the arrangement of your wires and fixtures on the site before purchasing them.
3-way Switch Wiring Methods
There are three main methods of wiring a three-way switch; namely the traveler system, the alternate system, and the carter system. Of the three methods, the traveler system is the most common and most flexible method.
The alternate system is rare while the carter system is prohibited in use in the USA. However, the carter system still exists in some of the very old buildings that were wired a long time ago when it was still in use.
Tip: Always mind safety – always turn off the power to any circuit you are working on before you start wiring, repairing, or replacing its fittings.
Traveler System Method (Standard)
This method of wiring a three-way switch has two traveler terminals and one common terminal. The use of the traveler terminals gives this method its name traveler system. However, since it also uses a common terminal it may also be referred to as the common system method.
The traveler system is the most common method of wiring a 3-way switch in the USA, UK, as well as parts of the world. This is mainly because this method is both safe and flexible. Its flexibility easily allows many different configurations of wiring a 3-way switch depending on the location of the power source and the light or set of lights.
Basically, in the traveler system method, the hot wire from the power source is fed to the common terminal of one of the switches. The hot terminal of the light fixture is connected to the common terminal of the second switch. The switches are then connected to each other by a pair of traveler wires via the traveler terminals.
Tip: For this method, interchanging the traveler wires between the traveler terminals of one of the switches will change the switch toggle orientation for on and off. That is, from the same orientation switch toggle to the opposite orientation switch toggle for on or for off.
As we have already noted, there are various configurations that you can use to wire a three-way switch. For the traveler system method, the choice of which configuration to use depends on the point at which power enters the wiring system and the location of the lights. Let us go through the common configurations you are likely to come across in the following sections.
3-Way Switch Wiring with Power at Switch (Diagrams)
(a) Light Fixture Last (at the End)
In this configuration, power first enters the first 3-way switch box, then to the second 3-way switch box, and lastly to the light fixture box. Diagram 1 below shows the arrangement of wires and light fixtures for this configuration.
This configuration requires a three-wire cable between the two switches and a two-wire cable between the second switch and the light fixture. The wiring procedure for this configuration using nm cables is as follows:
- Connect the black wire (hot) from the power source to the common terminal of the first switch.
- Connect the red wire and black wire (travelers) from each of the traveler terminals of the first switch to the corresponding traveler terminals of the second switch.
- Connect the black wire (hot) from the common terminal of the second switch to the hot terminal of the light fixture.
- Splice the ends of the white wire in each of the switches together using a wire nut and connect its end in the light fixture box to the neutral terminal of the light fixture.
- Connect the end of the green wire (ground) to the ground terminal of the light fixture.
- Connect a pigtail wire to each of the ground terminals of the two switches. Splice the ends of the green wire (ground) together with the other end of the pigtail wire using a screw nut in each of the switch boxes.
(b) Light Fixture in the Middle
In this configuration, power first enters the first 3-way switch box, then to the light fixture box, and lastly to the second 3-way switch box. Diagram 2 below shows the arrangement of wires and light fixtures for this configuration.
This configuration requires a three-wire cable between the first switch and the light fixture, and also between the light fixture and the second switch. The wiring procedure for this configuration using nm cables is as follows:
- Connect the black wire (hot) from the power source to the common terminal of the first switch.
- Connect the red wire (traveler) from the traveler terminal of the first switch to the corresponding traveler terminal of the second switch by splicing its ends in the light fixture box.
- Connect the black wire (traveler) to the light fixture and splice it with the white wire leading to the second switch and connect it to the other traveler of the second switch.
- Mark the ends of the white wire being used as a traveler with black tape so that you or other electricians that may do repairs afterward can notice it.
- Connect the black wire (hot) from the common terminal of the second switch to the hot terminal of the light fixture.
- Splice the ends of the white wire in the first switch box together using a wire nut and connect its end in the light fixture box to the neutral terminal of the light fixture.
- Connect the end of the green wire (ground) in the light fixture box to the ground terminal of the light fixture.
- Connect a pigtail wire to each of the ground terminals of the two switches. Splice the ends of the green wire (ground) together with each of the other ends of the pigtail wire using a screw nut in each of the switch boxes.
3-Way Switch Wiring with Power at Light (Diagrams)
(a) Light Fixture First (at the Beginning)
In this configuration, power first enters the light fixture that is situated at the beginning of the arrangement, then to the first 3-way switch box, and lastly to the second 3-way switch box. Diagram 3 below shows the arrangement of wires and light fixtures for this configuration.
This configuration requires a two-wire cable between the light fixture and the first switch and a three-wire cable between the two switches. The wiring procedure for this configuration using nm cables is as follows:
- In the light fixture, splice the black wire (hot) from the power source and the white wire leading to the first switch together. Mark this white wire with black tape.
- Connect the black wire (hot) from the common terminal of the first switch to the hot terminal of the light fixture.
- Connect the red wire and black wire (travelers) from each of the traveler terminals of the first switch to the corresponding traveler terminals of the second switch.
- Splice the ends of the white wire in the first switch together using a wire nut and mark them with black tape. Connect it to the common terminal of the second switch and mark it with black tape too.
- Connect a pigtail wire to the ground terminal of the light fixture. Splice the ends of the green wire (ground) within the light fixture box together with the other end of the pigtail wire using a screw nut.
- In the first switch box, connect a pigtail wire to the ground terminal of the first switch. Splice the ends of the green wire (ground) together with the other end of the pigtail wire using a screw nut.In the second switch box, connect the green wire (ground) to the ground terminal of the second switch.
(b) Light Fixture in the Middle
In this configuration, power first enters the light fixture that is situated between the first 3-way switch and the second 3-way switch, and then it enters each of the switch boxes. Diagram 4 below shows the arrangement of wires and light fixtures for this configuration.
This configuration requires a three-wire cable between the first switch and the light fixture, and also between the light fixture and the second switch. The wiring procedure for this configuration using nm cables is as follows:
- Splice the ends of the black wire (hot) from the power source and the black wire leading to the first switch together. Connect it to the common terminal of the first switch.
- Splice together the ends of white wires and also the ends of red wires that run between the two switches together within the light fixture box.
- Mark all the ends of the white wire being used as a traveler with black tape so that you or other electricians who may, later on, do repairs can notice it.
- Connect the red and white wires (travelers) from each of the traveler terminals of the first switch to the corresponding traveler terminals of the second switch.
- Connect the black wire (hot) from the common terminal of the second switch to the hot terminal of the light fixture.
- Connect the end of the white wire (neutral) from the power source to the neutral terminal of the light fixture.
- Connect a pigtail wire to the ground terminal of the light fixture box (if any). Splice the ends of the green wire (ground) from the power source and those from each of the switches and the other end of the pigtail wire together.
- Connect a pigtail wire to each of the ground terminals of the two switches. Splice the end of the green wire (ground) together with the other end of the pigtail wire using a screw nut in each of the switch boxes.
Other Methods (Non-Standard)
Alternate System Method
The alternate system method is known as the ‘California 3-way connection’, or ‘coast 3-way connection’. This method is no longer allowed if the neutral is not present in each switch box. Diagram 5 below shows a simple illustration of how this system works.
As the wiring diagram illustrates:
- The common terminals of each switch are connected together.
- The first traveler terminals of each switch are connected together and also to the hot wire from the power source (and also to the hot terminal of the receptacle when included)
- The second traveler terminals of each switch are connected together and also to the hot terminal of the light fixture positioned at one or both of the switches if so required.
- The neutral wire from the source is connected to the neutral terminals of the lights and also to the neutral terminal of the receptacle when included)
Diagram 5 below illustrates the alternate system method of wiring a three-way switch using nm cables.
Pros and Cons
One advantage of this method over the standard method is that you can connect a light, or set of lights at either switch in the same wiring system.
Another advantage of this system is that it allows for an unswitched load (for example a receptacle) to be connected near switch 2 (the further switch from the power source) without running as many wires as in the standard method.
Tip: When the switched light is close to switch 1 (near the power source) and a receptacle needs to be powered near switch 2 (further switch), this method will use fewer long wires than the standard method (four wires instead of five).
The disadvantage of this method is that when no unswitched load is required near switch 2 (the further switch from the power source), it will require more wires than the standard method.
Tip: When the switched light is close to switch 1 (near the power source) and a receptacle is not needed near switch 2 (farther switch), this method will use more long wires than the standard method (four wires instead of three).
Carter System (Old Style) Method
The carter system method is also known as the old-style method of wiring a three-way switch. This is an obsolete three-way switch wiring method that was used in the era of early knob-and-tube wiring. This method has been prohibited by the USA National Electrical Code since 1923.
Nevertheless, this wiring system may still be encountered in some very old electrical installations. Hence, some knowledge about this outdated three-way switch wiring method may still be useful in case repair or troubleshooting is required. Diagram 7 below shows a simple illustration of how this system works.
As the wiring diagram illustrates:
- The first traveler terminals of each switch are connected together and also to the hot wire from the power source (and also to the receptacle if required)
- The second traveler terminals of each switch are connected together and also to the neutral wire from the power source (and also to the receptacle if required).
- The light fixture is connected between the common terminals of the two switches, one to the hot terminal of the light and the other to the neutral terminal of the light.
Diagram 8 below illustrates how the carter system method of wiring a 3-way switch would be configured using the modern nm cables.
Pros and Cons
The main advantage of this method was that it used just one wire to the light from each switch.
Another advantage of this system is that it allows for an unswitched load (for example a receptacle) to be connected near switch 2 (the further switch from the power source) without running as many wires as in the standard method.
The disadvantage of this method is that in one of the four switch position combinations, both terminals of the light remain hot even though the bulb is not lit. The lack of a neutral wire to either of the two terminals makes this possible.
The fact that the light terminals can be hot while the light is not lit is a serious problem that poses a risk of electrical shock in the case you are replacing the bulb. This is the main reason why the method is prohibited in modern building wiring.
3-Way Switch Wiring Diagram Pdf Files
You can download our quality printable pdf files for all the three-way switch wiring diagrams in this post but for personal and educational use only. Kindly note that the diagrams are copyrighted and should not be published anywhere else whatsoever. The download links are under each of the diagrams.
Troubleshooting a 3-way Switch Wiring
Mostly, the cause of a circuit failure is a wrong connection and arrangement of the wires. Check that all the wires are correctly connected to the right terminals and that the contact points are firm enough in the whole wiring system.
For the standard (traveler) 3-way wiring system, ensure that:
- The hot wire from the power source is connected to the common terminal of one switch and the hot wire from the light fixture is connected to the common terminal of the other switch.
- The traveler terminals of one switch are only connected to the traveler terminals of the other switch. They should not be connected to any hot wires or to the load.
- The neutral wire from the source is connected to the neutral terminal of the load and nowhere else. In case it goes through the switch boxes, it should only be spliced together but not connected to any terminal of the switches.
Tip: In a standard 3-way switch, a neutral wire will not be connected to any of the terminals of the switch. However, some smart switches and timers may need the neutral wire to operate the switch.
For existing wiring systems, find out whether the connections are still intact. With the power off, check that all connection screws are still tight using a screwdriver, tightening them in case they are not. For connections that use clamps instead of screws, tug them to ensure that the wires are firmly secured on the clamps.
Tip: Over time, existing switches may stop working because they may get worn out or the terminal screws may get loosened.
In case you check and verify that you have wired the whole system correctly but the lights still do not work, the problem might be a defective three-way switch. In this case, you can test the internal functionality of the switch with a continuity tester (or multimeter on the Ohms mode) using the following simple procedure:
- Turn off the power, disconnect the wires from the switch and remove the switch from the circuit.
- Connect one of the meter probes to the common terminal and the other one to one of the travelers. Test continuity with the switch toggle flipped one way and then with the switch toggle flipped the other way.
- Now move the meter probe from one of the traveler terminals to the other traveler terminal and repeat the test.
The meter should show continuity with the toggle in one way and no continuity with the toggle in the other way in the test with each of the traveler terminals but in an opposite way.
In other words, if in the first traveler terminal test there is continuity when the toggle is up and no continuity when the toggle is down, then for the second traveler terminal test there should be continuity when the toggle is down and no continuity when the toggle is up. If not, the switch will be defective, in which case you will need to replace it.
Tip: This testing procedure is for standard three-way switches only. It will not work if you are dealing with a smart electronic switch or timer.
Repair & Replacement of a 3-way Switch Wiring
When repairing or replacing an existing three-way light switch, you need to be careful to avoid making errors that may cause the switch not to work.
Most importantly, ensure that you return the wires to the right screw terminals. This is especially crucial if you do not know the configuration used to do the three-way switch wiring or if standard wire color codes are not followed.
Before disconnecting the switch, identify the wires that are connected to each of the terminals. If the standard color codes are not observed, mark the wires, especially the wire connected to the common terminal, with pieces of tape differently.
You can now disconnect and remove the switch. To replace the switch, use the tape marks as a guide to return each of the wires to the correct terminal. For the travel system method, the wires connected to the traveler terminals can be harmlessly interchanged.
