How to diagnose a lightswitch that appears to do nothing

Question

Recently purchased property in the US, built in 1956. One bedroom has a lightswitch by the door that seems like it should control the ceiling fixture, but it doesn't. The ceiling fixture is a fan (with a remote, if it matters) and the fan can be turned on and off via the remote regardless of the switch position. So the ceiling fixture is always powered. I've also tested all of the outlets in the room and none of them are controlled by the switch. My questions:

1. Where do I go from here? I've been hesitant to pull the switch out of the wall to investigate because I don't know for sure what circuit it's on. I suppose I could just turn off the whole house to investigate safely, but I'm still not totally sure what I'm looking for.

2. My leading theories are that either the switch itself is faulty and stuck on, or the previous owner did some kind of bypass when the fan was installed.

Any thoughts on this?

UPDATE: Didn't have a ton of time last night to investigate, but I checked both plugs on all the outlets in the room, none seem tied to the switch. Still could be the tab. Removed the cover from the switch and at first glance it seems normal-ish. There's wiring in the box, and it connects to the switch. This is 1950s wiring so it's not super obvious at a glance which wire is which. I'll have to pull the switch out to tell more.

UPDATE Again: Found the breaker. The circuit contains quite a few things:

1. the bedroom ceiling fixture in question
2. all the outlets in the bedroom
3. a hallway ceiling light nearby
4. a bathroom ceiling light nearby
5. a GFCI outlet in the bathroom

The hallway and bathroom lights on the circuit have light switches that work correctly. The bedroom fixture is the only one stuck on. What's weird is it appears to be wired as a 3-way, see the pic. Bonus terrible rotted 1950's wiring insulation included. Am I interpreting that wiring wrong? Why does it look like a 3-way, but doesn't operate as a 3-way with any other switches? Anyway, next step is to check the receptacles on the circuit for any switched ones.

Although I'm beginning to suspect the switch is simply bypassed at the fan, apparently that is more common than I realized.

Answer 1

A switch is required by code in most places for most rooms - that way you automatically know how to easily turn on the light. But code does not (generally) mandate a particular lighting method, so many builders don't bother to put in the light fixture and just connect the switch to a receptacle for the homeowner to plug in a lamp. One of the first things I did after moving into my house (and I was not the first owner - people just don't realize they can change things, I guess) was to have ceiling lights installed in the bedrooms and connect the existing switches to them and disconnect the switches from the receptacles.

Three likely possibilities:

1. The switch was disconnected from whatever it originally switched. This could be an originally switched receptacle or it could be the ceiling fixture - e.g., to always be able to use the remote and not have a problem of being unable to turn it on with the remote because somebody had turned off the switch. If that's the case then if you open the switch you will either find no wires connected to the switch (i.e., disconnected from the switch and now bypassing the switch) or wires connected to the switch but none of them with any power (i.e., a non-contact voltage tester will show nothing on any of the wires).

2. The switch is supposed to control half of a receptacle. The receptacle was replaced at some time (to fix a broken receptacle, or for a different color to match new paint, or whatever) and the tab connecting the top & bottom hot screws was not removed.

3. The switch is supposed to control an entire receptacle. The wiring was redone at the receptacle at some time in order to make the receptacle always hot but the switch wires were left in place.

Answer 2

First, always search for switched receptacles. And here's the trick: Receptacles can be split so each of the 2 sockets is controlled independently. So it's not enough to plug into one socket, throw the switch, cross it off the list. If you do, you have a 50/50 chance of missing it! You must try each of the 2 sockets separately.

Second, if the switch is wired to switch a receptacle, and that receptacle has been split, and someone later came along and changed the receptacle (typically for aesthetic reasons) and they didn't know what they were doing, then they defeated the switch by failing to remove the tab which splits the receptacle. In that case you will find (or not find) wiring in the walls that will allow that switch to start working again. Unlikely as this seems, we see it all the time around here.

• Note that if the switch controlled BOTH a split receptacle AND a ceiling light, and the "novice receptacle changer" did the above, that would also cause the light to stick on and refuse to be switched. That might just motivate someone to install a light with a remote!

Third, if the fan is controlled by remote, they might have deliberately wired the fan or switch to bypass the switch altogether. That way the remote always works and they don't have to get annoyed and go over and throw the switch half the time.

Answer 3

If you've checked all the lights and all the outlets, and you still want to figure out what this switch does, if anything, the next step is to use a toner (variously called a wire toner, electrical toner, wire tracer, tone and probe set, probably other variations). This is a 2-part device: one part clips on one end of the wire and injects a modulated tone. The other part is essentially a special purpose radio tuned to listen for the injected signal. The receiver has adjustable sensitivity so you can reduce the sensitivity as you get closer.

Most likely you'll then be able to trace the wires to an electrical box that was to be controlled by the switch. Perhaps someone decided the switch was unnecessary and just capped off the wire and left it disconnected, or perhaps it was rendered ineffective by improperly installing an outlet as others have described.

Of course you'll want to do this safely, turning off power first and verifying it's off with an appropriate tester. If you turn off switches, breakers, or fuses, mark them so someone else doesn't come along and turn them back on. Also look for a toner that's rated for mains voltage so you know it won't fail in some hazardous way if there's a mistake.