Expert: Bob Sponaugle - 9/6/2007

Question
QUESTION: The existing light switches have four wires coming to four screws on the sides.

The newer style replacement rotary dimmer switch has four wires coming out of the back.  There is no indication on the wires at the old switches that will let me figure out which color of wire corresponds to which screw.........

I've gotten a couple of books out of my personal library and the local lending library - but without a way to tell what green, red, etc. "mean" in the way of incoming hot wire, etc. I have my doubts about switching things out without causing myself more trouble than I want to deal with.

ANSWER: Hi.

The dimmer green wire is the ground. It connects to the bare wires.

The other dimmer wires should have two wires one color, and one wire another wire.  The old switch had two terminals one color and one terminal another color (not counting the green ground screw).  The wires that came off the two terminals the same color go to the 2 dimmer wires that are the same color.  

Hopefully you did not unwire everything.  If you did, try to find the two insulated wires that come out of the same cable to put on the two wires that are the same.

Remember, you can use only one dimmer, the other has to remain a toggle switch.

I hope this helps.

Bob

---------- FOLLOW-UP ----------

QUESTION: One is paired up black and red - the other is paired up black and green.  I have a diagram (emailed) from the manufacturer........

I'm starting to think that a circuit tester is on my shopping list for myself (I'm not waiting for Christmas, Mothers' Day, or Fathers' Day Sales...........).

It's raining right now so I'm not messing around with the circuit breaker box until the ground is a bit drier......

I have been shocked when working with low voltage door bell chimes.........that was enough to let me know that I didn't want to try working with higher voltages on an open circuit.  You can't be too careful when working with electricity!

Answer
Hi.

Wire colors, other than the green ground really doesn't mean too much with 3 way switches. There is also a lot of combinations of wiring, depending on the relationship between the power source, light, and switches.

But let me give you a little background about 3 way switches:  The two terminals that are the same color on each switch are for the traveler wires.  These are 2 wires that go between the two switches, so they can talk to each other.  That leaves one terminal left on each switch.  One is the hot power in, the other is the hot power out that goes to the black fixture wire.  The neutral wire bypasses all the switches.

The traveler wires are likely to be in a cable with a total of 3 wires (not counting the ground), and one traveler wire could likely be a red one.

I hope this helps.

Bob