BristolUK

We have four sets of 3 switches in our home. One set by the main bathroom door is for the bathroom light, the landing lightand the bathroom fan.

There's another set by the back door. One for the kitchen light, one for the external lights and one for who knows what. I had thought it might be the external socket but that works regardless of the position of the mystery switch

Two other sets of 3 have 2 controlling different lights and the third does nothing.

So that's a switch on each of three sets that does nothing.

Are they just spares in case of any additions? Or when they were installed there was a special offer on threesomes instead of pairs?

Danny B

Have you unscrewed the wall plate to see if there are any wires connected to the mystery switch? We had a mystery switch by the front door, it took us until we installed the outdoor Christmas lights to figure out what it is for.

Zoe Bell

Are you sure they don’t control any of your plug sockets.? It’s common in Ontario for them to,control a socket that you are meant to plug a lamp into

Pulaski

I have almost the same, in three different locations around the edge of the living room - one next to the door into the kitchen, one just behind the front door, and one in the end of the hallway - so all are close to the living room but are otherwise about as far apart as possiible.

I couldn't fathom what they were for, but had contact information for the previous owner. I emailed her but she didn't know and had never found what they were for depsite living there for 15 years and having had the house custom built for her and her husband.

Each of the switches is connected to a live wire that has 37 volts in it, so about 1/3 of mains voltage! I asked an electrician, but he had no ideas and said he had never heard of such a thing.

So I removed the "spare" switch (one of two) by the kitchen door, and bought a "switch and blank" face plate to cover over the space where there had been a switch. The switch behind the front door was on it's own, so as I was reconfiguing the wall and closet layout I just removed the switch, capped off the wires, and was planning to just cover over the location with the drywall. The third switch was like yours - one of three, and so I have never bothered to remove it as getting a suitable face plate would be difficult.

Anyway, so I carried on with other repairs I was working on, then I discovered that the well pump had stopped working, and as I hadn't been working on the pump or plumbing I was at a loss to know why the well pump had stopped working? I checked the breakers, and checked the electrical connections at the well head, but found nothing. I went through everything I had done that might have affected the well pump, and drew a blank, then I went through everything I had been doing ..... and then it hit me - the mystery switch! I reinstalled the switch, connected to 37v power, and the water started flowing again! And the well pump works on 240v, so I have no idea where the 37v came from or how the switch affects the well pump. And it doesn't make any difference whether the switch is "on" or "off" the well pump works either way - it is apparently only necessary that the wires are connected to a switch. In the end I pulled the wire up through the ceiling and reattached the switch, and so there is, to this day, a "necessary" switch above the ceiling.

scrubbedexpat091

Our old place had a switch I never could figure out what it controlled if anything, it had wires going into it, it was a double side by side, one controlled the ceiling light, but the other one, no clue. I tried every outlet with a fan and the switched controlled none of them.

It perplexed me for 3 years.

BristolUK

Knowing me I'd not get them back on properly.
But if I did discover some wires that would turn into a major worry

Yeah, I'm familiar with that. One of the bedrooms has wall sockets controlled by what looks to be a light switch . My laptop would keep going to battery if it was the same thing

No well here. We do have an outlet on the patio, down from the deck but that doesn't work on or off. I thought the spare in the kitchen might turn on the external lights on the garage but no.

Ad then what happened...you moved?

scrubbedexpat091

Yep moved.

Maybe the new tenants in that unit will have better luck with that switch.

BristolUK

It would be funny if they randomly turned things on and off in other people's homes.

Pulaski

My guess would be that the switch was wired for a ceiling fan - you would have had to remove the light fitting to see if that was the case, but if so you could have had a combined light and fan with separate switches, instead of a master switch and having to use the pull chains to control the lights and fan.