I am trying to replace an old ceiling light fixture. The old chandelier could be turned on from three different places: a light switch near the door, one near the kitchen, and another at the top of the stairs.
In the ceiling junction box are 2 red, 2 white, 2 black and 1 ground wires.
The new light fixture only has two wires – both black. One is ribbed – which I am assuming is the "white" wire.
I have tried multiple combinations – and can only get the light switch near the kitchen to turn on the light.
Please help!
Best Answer
This one's more than a little tricky. But let's start by reviewing how 3-way circuits work in the first place.
(And by the way, you didn't make life any easier on yourself by unhooking all the wirenuts in the box. The right way to do this is only unhook the 2 wires that were hooked to the old light, aside from ground.)
So here's a basic 3-way circuit. Now I am a huge fan of identifying wires by color. I use wires in conduit, so I get to do that. With black-white-red cable, you can accomplish the same thing by marking both ends of the wire with colored electrical tape. I strongly recommend labeling as you figure out the circuit, and then always thereafter.
Note that between the 3-ways, is "/3" cable (3-wire) cable. This is to accommodate a special rule: In any cable or conduit, currents must be equal. If one of the travelers is taking power to the lamp, the power must return via the neutral in the same cable etc. That's why I drew it very thin with wires bunched.
This isn't your circuit, though. Yours is a little more complicated because with 3 control points, it must involve a 4-way switch (UK:3-way). But not that more complicated: take a look.
You can see I've moved the bulb, but it's just cosmetic; it doesn't really affect the circuit any. And the 4-way just goes mid-line along the two travelers - inputs 2 travelers, outputs 2 travelers. You can have as many 4-ways as you please, just like that. I just left the second set of travelers yellow... it's not that complicated. Note the screw colors (brass/black).
Now. Imagine the first 3-way (and the passthrough neutral) is in a box. Imagine the bulb and 2 yellow messengers passing through) are in another box. Imagine the 4-way (and passing through switched-hot) are in another box. That is exactly how your house is wired.
In this drawing I changed the second set of travelers to blue, supply hot to brown, neutral to gray and switched-hot to orange. Never mind that, though.
Physically, it'd look like this if we color-taped all the wires (a lot). Note that in the /3 cable, the underlying hard colors used in your house could be absolutely anything.
Though I cannot say whether the bulb is left or right of the 4-way -- as you can see from the drawing, it changes very little either way.
So now you have some detective work to do. Take apart your switches, but don't remove any wires :) Among your switches:
It's also remotely possible that the power supply enters the 4-way box. Let me know if that's the case, it makes the drawing slightly different, but not shatteringly so.