dualing light switches

November 5, 2010 10:36 PM

Two sets of dual light switches control two lights at the top and bottom of my staircase. One switch on each set stopped working, why and how can I fix it?

Last night before going to bed I flicked the switch to turn off the light at the bottom of the staircase. Only I accidentally flicked the switch for the light at the top of the stairs and saw a spark which I thought came from the light bulb. I figured the bulb had burnt out because the switch no longer activated the light. This sucks because I'd need a ladder to reach it, which I don't have. Next morning my partner gets up first and finds that the light at the top of the stairs can still be turned on by the switch at the bottom. So now the current status is that there is one working switch at each end of the staircase controlling one light each, where there used to be two switches at each end controlling both lights.

So my questions are: what happened, how can I fix it, and how did the darn thing work to begin with?

posted by wigner3j to home & garden (6 answers total)

If you have to ask that question, then the answer is "You don't fix it. You call an electrician."
posted by Chocolate Pickle at 11:14 PM on November 5, 2010

Definitely some bad wiring. I don't really follow what you're saying switch and light wise. It sounds like it might be as simple and a "jumper" wire between two switches, but again I don't think I understand the setup. If you're lucky you live in a recently built house and your wiring is run through conduit. Find the wiring that has some insulation burnt off and shorted out, pull new wire, and replace.

In general I don't ever mess with gas or electric, but I just had an electrician over to correct a similar thing, and it was really easy. Part of an old wire had lost it's insulation and shorted out to the conduit. If this is not up to your spec, call an electrician and just ask their call rates. Find the cheapest one, because this will take him literally 10 minutes to fix. You'll learn a lot and be able to do it yourself next time.

When I called the guy quoted me $80 an hour, which sounds outrageous, until you realize you know nothing about electricity or wiring except theory and what you have read in an ld Sears book. I helped him run new wire, install a new breaker switch and even hook up a new switch for a new light, and all he charged me was labor. The parts and wire were negligible. I think he wanted someone to commiserate with on our local football team more than he wanted to charge for a $1.50 light switch.
posted by sanka at 11:23 PM on November 5, 2010

To recap: Normally switch A at the top of the stairs and switch A' at the bottom of the stairs control light A" over the stairs. Also switch B next to A and switch B' next to A' controls light B". Something happened and now switch A and B' do not toggle the status of their respective lights; only A' and B can turn their respective lights off and on.

Sounds like you have two sets of three way switches. A and B have probably shorted in some way (either internal to the switches or something has jumpered the switches) making them invisible to the switching circuit.

Easiest thing to do would be to turn off the breaker servicing the light then take the cover plates off the defective switches. You'll probably see something shorted out either immediately or when you pull the switches out of the boxes. The fix would be to resolve the short. There are about a dozen distinct ways this circuit can be wired so without knowing where the line comes in or where the lights are located (electrically speaking) respective to the switches it's tough to suggest a more detailed course of action. If the problem isn't obvious identify all the wires entering each switch box and light fixture and how they are connected then post a description of your exact setup. Note that the 3 way switches should have a common identified with either writing or a different colour (usually black) screw or both. It's very important to identify this terminal and make note of which wire goes to it.

As a strictly WAG: sounds to me that that two circuits are wired mirrored to each other so that the switch leg of the A circuit is connected to the switch in the same box as the hot leg of B circuit and some how these have come into contact with each other.

Or: the two sets of travellers in the box at the top of the stairs are contacting each other.

Note: the NEC apparently requires white travellers to be identified with black markings. Canadian code does not require this (it actually discourages it for house wiring) and I bet it isn't done in many cases in the States as it would be an easy thing to slack off on.
posted by Mitheral at 11:47 PM on November 5, 2010

Seconding Chocolate Pickle, seriously get professionals involved.
posted by Confess, Fletch at 7:05 AM on November 6, 2010

Okay, I am an idiot. I woke up sober this morning and realized there is in fact a third light. One light at the top, one at the bottom, and one in the middle. The one in the middle is only controlled with a switch at the bottom of the stairs, the others can be controlled at either end. The bulb at the bottom burnt out and at the time I forgot about that light and focused on my inability to control the light in the middle with one of the switches at the top of the stairs. I replaced the bulb and all is fine except for my ego.
posted by wigner3j at 7:52 AM on November 6, 2010

I second Mitheral's comments: these are three-way switches. If you do not feel comfortable changing a switch out, then do call an electrician, or at least a competent handyman. If the wiring is off then the switch out will not solve the problem.
posted by wylde21 at 2:11 PM on November 6, 2010