The diagrams below show the conventional wiring for 3 way switches. Typical 3 way switch wiring nm cable.
Unfortunately not all 3 way switches are wired.
3 way switch light wiring diagram. In wiring three way switches the power wire is connected to the common terminal usually marked com. This diagram sh ows connections when the power comes into the first switch on to the second switch and then on to two or more lights switched by the 3 way circuit. Hook the curled end of the wire under the screw then tighten down the screw to hold the wire firmly in place.
This screw is usually in the upper left side of the switch and is painted black but check the guide that comes with your switch. A 3 wire nm connects the traveler terminals of the first and second 3 way switch together. Here we have a 3 way switching lighting circuit sometimes called two way switching with intermediate.
This allows a single light to be turned on or off from any of the switches. 3 way switches are used to control lights with two switches. This method might be used when power is available in the ceiling but switch boxes are on opposite walls it is often easier to run the cable up into the ceiling light box instead of between switches.
Two wire cable runs from the light to sw1 and 3 wire cable runs between sw1 and sw2. 3 way switch wiring with light first. In this 3 way switch wiring diagram the power in line enters the light box but 3 rope cables are then installed between the light box and each switch box.
Note that this configuration is easiest to do when utilizing the first method of 3 way circuits discussed previously in our wiring a basic 3 way switch article or diagram. These switches do not have an on off position like single pole switches. This page shows it wired in the old cable colours if your house has the new colours you want to go here.
In the 1st diagram below a 2 wire nm cable supplies power from the panel to the first switch box. 3 way switch diagrams for multiple light fixtures. If not marked the common terminal may be color coded black or brass.
The 3 wire cable consist of a black wire a white wire and a bare copper wire while the 4 wire. Attach the black power cable from the wall to the general screw black in the three way light switch. When wiring a 3 way switch circuit we will be using a 3 wire cable known as romex coming from the source such as the breaker box.
In the following illustrations track each wire with a finger. It is true that there are several wiring configurations for wiring 3 way light switches and all of the wiring configurations will depend on where the incoming circuit power is located and once that is identified the rest of the three way wiring connections are straight forward. It is important to understand how these are wired before attempting to troubleshoot or replace.
The black line wire connects to the common terminal of the first 3 way switch. Then a 4 wire cable going between the two 3 way switches and then a 3 wire cable going from the switches to the load. In this diagram the source for the circuit is at the light fixture and the two switches come after.
The location of this common terminal may vary according to the manufacturer of the switch.