With a flip of a switch, DIY license is at stake

DEAR TIM: Well, now I’ve done it. My newlywed wife has lost all confidence in my home improvement skills. She wanted me to install a dimmer switch in our dining room and now the chandelier only works half the time. There are two switches in the room that control the light. They worked fine before I started the job. But now you can only get the lights to come on at one switch. Can you help me out of this mess so she lets me touch a putty knife in the future? What did I do wrong and how in the world do these crazy three-way switches work? – Brad G., Hamilton, Ohio

DEAR BRAD: I’ll never forget the day I almost lost all my home improvement privileges from my new wife. We’d been married about three years, and I was replacing an ivory wall receptacle in our kitchen with a white one. Kathy said, “Shouldn’t you turn off the circuit breaker before you do this?” I responded, “No, that’s only if you don’t know what you’re doing.”

Seconds later there was a flash, and small droplets of molten copper and steel made burn marks in our new gleaming white laminate tops. Kathy was furious and has never let me live down that mistake. I was too lazy and cocky to go downstairs to turn off the breaker. Believe me, you make that mistake just once. I was very lucky to avoid electrocution and serious burns.

If it’s any consolation, you’re not the first person to goof up the wiring a set of three-way switches. It’s easy to do if they’re not marked, and most electricians never mark the wires. What a shame, because it would only take a few moments to do this.

I had an interesting experience last summer that really helps me explain how three-way switches work. I became a certified train conductor working part time on a scenic train in New Hampshire. Part of my training included being a fireman on the train. When you’re a fireman, you have to throw the switches to allow the train to go on different tracks.

When the train approaches a switch, it’s going to go down one track or the other depending which way the switch is oriented. The same is true inside a three-way switch.

If you look at the first three-way switch that’s connected to the wire that leads back to your electric panel, you can see why the light goes on or off. If you flip the switch one direction, you stop the electricity from entering the rest of the switch circuit.

If you flip that first switch so the light comes on and then walk over to the second three-way switch and flip it, the light goes off because you have oriented the switch so the electricity can’t travel down the wire that’s connected to the chandelier. It’s caveman simple when you think about it.

Here’s what you need to know to get back in your wife’s favor and to get the chandelier working perfectly. First, turn off the circuit breaker that powers this circuit. Don’t be bold like I was all those years ago.

Inside each box you should discover four wires that connect to each three-way switch. One wire at one of the switches is the continuous hot wire that is getting electricity from your circuit breaker panel. At the other switch box there’s a wire that goes to the chandelier.

At each switch box you now have three remaining wires. One wire might be bare copper or have green insulation on it. This one is the ground wire and connects to the green screw on the three-way switch. The remaining two wires are called travelers and simply extend to the other three-way switch.

Look at your new dimmer switch or a new three-way switch. You should notice four screws, two on each side. One is green; that’s the ground screw. One screw is black and the other two are brass colored. The black screw is the important one. You connect the continuous power wire to this screw in the one box and in the other box you connect the wire that goes to the chandelier to the other black screw of the second three-way switch.

The leftover wires in the box connect to the two brass screws. It doesn’t matter which of the wires connects to each of the brass screws. Do this and your chandelier will work perfectly again.

The issue you’ll have is determining which of the wires at each box is the one to connect to the black screw. If you use a simple multimeter that can tell you voltage and continuity, this will be child’s play. Using the multimeter at the one box will allow you to discover which of the wires is the continuous hot wire that has power when the circuit breaker is on. Mark this wire once you determine this.

You can then use the multimeter’s continuity tester along with a scrap piece of wire that stretches between the two switch boxes to determine the two traveler wires. By connecting the scrap piece of wire to one of the wires at the other switch the tester will tell you if you have continuity. Once again, mark the wires with a T1 or T2 telling you they’re the travelers. Do this in each box. The remaining wire in the second box is the one that leads to the chandelier. It’s easy!