The following article explains how to perform three way switch wiring when the power source is at the fixture.
Three way switch wiring power at light.
With a pair of 3 way switches either can make or break the connection that completes the circuit to the light.
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.
The hot from the power source connects to the common terminal of the first 3 way switch sw1 and the neutral is spiced through sb1 to the second 3 way switch sw2 via the 3 wire cable c2 that also carries the travelers that connect the two switches where it is spliced through sb2 to the neutral terminal of the light.
The existing 2 wire black and white romex can still be used to connect a 3 way switch 2 and the light fixture.
Mike teaches you how to wire a 3 way switch.
If your 3 way light switch 2 is connected between the power supply and the light fixture as is most common.
Two three way switches control one light with the electric power coming through the first switch flowing to the second switch and then to the light fixture.
The correct wire must be connected to the common screw of a 3 way switch otherwise the switches will not control the light fixtures correctly.
Below is a simple 3 way schematic that can be applied to all three way electrical light switch connections.
This is only a wiring schematic and not the actual wiring method used for 3 way switch installations.
In this light switch wiring diagram the power feed joins the circuit via the light fixture where a two wire cable c2 runs from the light to the first 3 way switch sw1 and a 3 wire cable c3 joins the two switches.
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Two very old three way switches.
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.
Two very old three way switches are depicted in the photo above.
3 way switch schematic wiring diagram.
Each 3 way switch in these examples are controlling the power source to the same load.
Wiring a 3 way light switch.