Three-way switches allow for controlling a light fixture from two separate locations, these are usually used at the top and bottom of a flight of stairs or at two different entrances to a room. On this page are several wiring diagrams for 3 way switch lighting circuits depending on the location of the source with relation to the lights.
Also included on this page is a diagram for a 3 way dimmer, an arrangement to control a receptacle from two locations and one to add an always-hot receptacle outlet to the circuit. For more information about wiring these circuits and troubleshooting tips check below.
It is the responsibility of the user of this information to know and understand the NEC (National Electrical Code) as it applies to them, as well as any local regulations or laws that may pertain. While many jurisdictions do adopt the standards of the NEC, some may have requirements in addition to, or exemptions from those standards.
The information on this page is intended to aid in electrical wiring projects that become necessary when doing DIY home improvements and repairs. Some of the diagrams here are for older circuits that may not adhere to the latest code updates. When running a new circuit be sure to use the latest approved wiring arrangements. We cannot assume responsibility for personal injury or property damage as a result of using the information provided here.
In the diagrams on this website the brass colored terminals on the devices represent the hot side of the circuit and the silver colored terminals represent the neutral side. Green is used to denote ground wires and terminals. Not all outlet boxes or older devices will have a grounding terminal. When running new wiring the ground wires should be spliced with a short piece of wire to connect to each device that has a grounding terminal, and to any grounding terminals in the outlet boxes. Also be aware that the white wire may be use to carry current in some household circuits, in these cases it should be marked with black electrical tape to indicate it is hot.
In this diagram the electrical source is at the first switch and the light is located at the end of the circuit. Three-wire cable runs between the switches and 2-wire cable runs to the light. The black and red wires between SW1 and SW2 are connected to the traveler terminals. The hot source is connected to the common terminal on SW1, and the common terminal on SW2 connects to the hot terminal on the light.
The source in this circuit is at the first switch and the light fixture is located between SW1 and SW2. Three-wire cable runs between each switch and the light fixture. The hot source wire is connected to the common terminal on SW1. The common terminal on SW2 is connected to the hot terminal on the light. The traveler wires are spliced at the fixture box to run between the traveler terminals on the switches.
In this diagram the source for the circuit is at the light fixture and the two switches come after. Two-wire cable runs from the light, to SW1 and 3-wire cable runs between SW1 and SW2. The hot source is spliced to the white cable-wire, which is wrapped with black tape to mark it as hot and run through to SW1 where it is spliced to the black wire running to the common terminal on SW2. The hot terminal on the light fixture is connected to the common terminal on SW1. The red wire and marked white wire travelers connect the traveler terminals between the two switches.
The following 3 diagrams show the wiring for a specially made dimmer that can be used in these circuits in place of either of the the 3 way switches or both. This arrangement allows for lowering the lights in a 3 way circuit. After the dimmer level has been set the other switch will turn the lights off and on at that level. This device can be used in place of any of the 3 way switches in one of these circuits, as well as to dim the lights in a 4 way circuit.
Instead of terminals, a 3 way dimmer has 4 wires coming out of the casing: one common, two travelers and one ground wire. The common wire is usually black and the travelers red. In any case, the traveler wires will usually be the same color to distinguish them from the common wire.
In this circuit the source hot is at the common on the 3 way switch and 3-wire cable runs from there to the dimmer. The traveler wires run between the 2 switches and 2-wire cable runs from the dimmer to the light. The neutral from the source is spliced at each box to run through to the neutral terminal on the light fixture. The common on the dimmer is connected to the hot terminal on the light fixture.
This diagram is the same as the one above but the dimmer comes first in the circuit. This arrangement is provided for easy reference when dealing with a circuit wired like this.
In this arrangement two 3-way dimmers are used to allow for lowering the lights from both locations. Here the common on the first dimmer connects to the hot source and the common on the second connects to the hot on the light. As with all these types of circuits the traveler wires run between the switches and connect the traveler terminals.
This diagram shows the wiring to control a receptacle outlet with two 3 way switches. The source is at SW1 and 3-wire cable runs between all the devices. The hot wire from the source connects to the common terminal on SW1. The common on SW2 is connected to the hot terminal on the receptacle. The traveler wires are spliced in the receptacle box to run to the traveler terminals on each switch. The white cable wire is used as a traveler to SW2 and marked hot with black tape.
Here a receptacle is added to the circuit before the first switch. It is not controlled with the switches but is instead always hot. The source hot, neutral and ground are spliced to a 2-wire cable that runs to the new outlet. The 3 way switches and light are then wired in the usual way with the common on SW2 spliced to the source hot and the light hot wired to the common on SW1.
Modern three-way switches have 3 terminals to carry circuit electricity and one terminal for a ground wire. Older devices will not have a grounding terminal. Of the three circuit terminals, one is called the common and the other two are known as travelers. The common terminal may be labeled and is usually a different color than the traveler terminals. Depending on the manufacturer, the travelers may be on opposite sides of the device or the two terminals may be on the same side. In any case, the common terminal will be distinguished from the travelers in some way.
The common terminals will always be connected to a hot wire, either from the source or on the light fixture. These connections can be reversed if it's more convenient, as long as one of the 3 way common terminals connects to the hot source and the other one connects to the hot on the load, these circuits will work properly. The traveler terminals will always be connected from switch to switch. Travelers never connect to a device load or to a source wire. It doesn't matter which traveler terminal is used for which traveler wire, reversing them should make no difference.
If your switches stop working they may be worn out or the screws may have come loose. If you've wired a new switch correctly and the circuit still doesn't work, the switch may be defective. Check that all connections are tight and test suspect switches with a continuity tester or multimeter set on the Ohms setting.
If the switch is good make sure the hot wire from the source is connect to the common terminal on one of the 3 way switches and the hot wire to the fixture is connected to the common on the other. Likewise, be sure the traveler terminals are connected between switches only, and not to any hot wires or the load. Also be sure the neutral from the source is connected to the neutral terminal at the light. A neutral wire will usually not be connected to the switches in these circuits, although some remote controlled switches may make use a neutral wire to operate the radio receiver for the remote.