Gayle: You really need to fix that ceiling light in the dining room.
Tom: Really? We’ve lived here for years, hon, and that light works just fine.
Gayle: You just ignore the problem. One wall switch turns the fixture on and off, but only if the switch on the other side of the room is in the up position. If that switch is down, the light won’t work.
Tom: Well, I guess I’m just used to walking across the room and trying both switches until the light comes on. It must have been done by the guy who owned the house before us. Is it really that big a problem?
Gayle: Well, no, but you’re a fix-it guy, and I’d expect everything to work well in your home. Right?
Tom: The problem is the switch. Someone substituted a single-pole switch for a three-way switch. Let’s look for markings on the switches. Ah, yes. One switch has “ON-OFF” marked on it and one has no marking. The switch with no marking is the three-way switch.
Gayle: Now you’ve got me confused. Two switches control the light. Why do they call it a three-way switch?
Tom: It’s named for its three terminals, not counting the green ground screw: one common terminal and two “traveler” terminals. What matters is that if you want to control one light with two switches, both switches must be three-way switches. Makes sense, doesn’t it? A three-way switch has a power connection and an additional power/switched connection, so they throw power back and forth between the switches. You also need an extra wire between the switches to make them work. In our case, the switch marked “ON-OFF” needs to be replaced with a three-way switch, if the extra wire is in the wall. Got the switch-switch?
Gayle: Well, it would be great if you could switch the switch for the proper three-way switch. Thanks, honey.
Tom: I’ll give it a try, but if the wiring isn’t there, or if there’s a pile of wires inside the switch box, we’ll be calling an electrician. I don’t mind doing very simple electrical work, but when it gets confusing, we need an expert.
Gayle: Great. You know we need that exterior GFCI replaced, the garage light near the door opener keeps burning out bulbs, and I really want a new ceiling fan in our bedroom. Let’s call an electrician.
Tom: Great idea. (Under his breath) And a little less fix-it work for me around here. I’ll call the electrician I know, and we can work on lining up the parts and fixtures we’ll need.
More on this: Three-Way vs Two-Way Light Switch, Quick Tip #16
Tom Feiza, “Mr. Fix-It,” is a professional home-improvement expert. His wife, Gayle, keeps track of the couple’s lengthy to-do list. More fix-it advice appears on Tom’s website at misterfix-it.com.