My hunch for three gang switches with only two working switches is that the installer used a three gang because he hand it handy . Forget to mention…I can’t find my natural gas inlet. Mine is the only house on the block without gas, and I have an outdoor meter. I think the former owner his it when he switched to an electric stove. I asked the town and gas co. And they quoted approximately 20k to bring gas back to the house. Uh, no.
I live in a historic district, in an older home. The previous owners were into what’s called “sport wiring”.
After living there several years, I had a couple of non-functioning switches in the living areas pulled and covers put over the gaps (according to code). It just annoyed me that those switches were-or were not doing something. I disconnected them and moved on with my life.
I have some extra switches in the basement that I’m pretty sure control some grounded plugs in a crawl space. Why there are grounded plugs in a crawl space, and why you’d want to turn them on and off, no idea.
A bazillion switches in the house, and yet I can’t turn the yard light on or off.
Exterior outlet? Maybe in the soffit for Christmas lights?
My son bought a house that had a very neat secret door. It looked like a bookshelf but swung out. But it was a really substantial bookshelf that looked like no way it would swing out.
Unfortunately it was kind of hard, actually, to get it open. Also unfortunately, it led to the laundry room. You want a somewhat easier door o the way into the laundry room, not to mention one that opens wide. So now there’s another door.
You want weird electricity stories, I’ve got 'em. Every single house I’ve owned has had electrical, um, issues.
Usually it’s just wiring that connects where you wouldn’t think or switches that don’t turn anything on. In my last house I had a doorbell that would work for awhile, and then wouldn’t, and nobody could figure out why. (By “nobody” I mean everyone who lived there plus one electrician.)
But the weirdest was, we had just moved into this place. I plugged a lamp into a socket and switched it on. Nothing. I looked for a wall switch that might be connected to that outlet. Nothing. My husband said we’d have to use an extension cord and plug the lamp in to the next closest switch. He stuck the extension cord into that other outlet–now, mind you, nothing else had changed, the light was still plugged into the first outlet only now there was an extension cord plugged into the other outlet but connected to nothing, yet–and the light came on.
The weirdest thing about this was that my husband, who is not an electrician, figured out why that happened. He explained it to me but it made no sense to me so I’ve forgotten.
My House:
Only one strange thing going on when I moved in. After a few days the garage door stopped working. Some poking around with a meter revealed that the dumbass who lived here before me wired it into the porch lights. When I turned off the porch lights a few days after moving in (I mean, why were they on), the door stopped working. I left them on for about a year before rewiring it. It was literally a 10 minute project, took about 18 inches of wire and wasn’t done properly because dumbass was a dumbass. The wire was right there, installed by the builders, but he just didn’t see it so he did something stupid instead.
My Ex-grandfather-in-law’s house: He was a EE by trade and a tinkerer on the side. He added a water meter to his water heater to see how much hot water he was using. He ran water pipes (before the water heater) up to his roof and installed his own solar panels to pre-heat the water back in the 60’s or 70’s. But this thread is about electrical stuff. There were so many switches and lights in that house. I remember one of the switch plates in the kitchen had two regular switches and then a bunch of various size lights on it. I asked another family member about it and the best answer I got was “I think one of them turns on when the washing machine is done”. Meh, it’s what he did, it kept him happy. I wasn’t around when they moved him out of the house so I don’t know if they left it for the new people or tore as much of it out as they could find.
As for secret doors, I um ‘don’t know’ someone that had a secret door down in his basement for doing secret stuff. My understanding was that if you didn’t know that door was there, you wouldn’t know that entire wing of the house even existed…until the night he fell asleep with a cigarette in his mouth. The fire department found his secret room and his life changed that night.
(‘doing secret stuff’ sound bad. It was a really major grow operation)
I’d be willing to bet that’s an EPO or Emergency Power Off for the room.
The last house I lived in had a switch in the upstairs hall that did nothing at all. Once I got curious enough to look at it, it turned out to be a four-way switch that probably broke long ago and the wires had been disconnected from it and wire nutted together so the other three-way switches would work.
This house is festooned with mysterious wiring. Apparently, there used to be a pool here, as at a back corner, there’s a collection of outlets, boxes, weatherproof switches and a big timer. None of it does anything now. The builder was also nutty for outlets - there are fourteen outlets in the garage, six of which are in the ceiling.
We had a “mystery switch” next to the sink, exactly where you would expect a switch for a garbage disposal, except there was no garbage disposal and, since we’re on a septic system, can’t have one.
One day while walking in the woods on the south end of our property I found a halogen flood light sticking out of the ground! Turns out the previous owner had a flagpole down there and the switch next to the sink controlled the light for the flag.
Hey! What are you doing in my parent’s house?
There is a single switch in my second bedroom. There is no overhead light. The siwtchis not connected to any of the outlets. So I have no idea what it is for, except to support a cute switchplate holder.
It’s a doorbell. Have someone stand next to it while you ring the doorbell and see if the sound comes from it. If not, it’s no longer active and your bell is elsewhere (if you have a working doorbell at all).
If it doesn’t do anything, see if you can pop the cover off: it could be a battery powered one that uses wireless doorbell that has long been tossed. That’s the way the new ones are.
Well, the doorbell it is, then. I don’t think I’ve ever lived in a house where the doorbell chime was that visible, but then I don’t think I’ve ever lived in a house quite this old (according to a local real estate agent’s website it was built in 1954, and from Googling it the bell was probably installed when the house was new.) For that matter, the front door doesn’t have a modern peephole, either - just a little metal door at eye level that opens from the inside, with a little metal grate that lets both you and your caller see each other.
And then there’s the laundry room, where the waste water from the washing machine drains into a big uncovered hole in one corner of the room, which has a pipe leading upwards out of it that I assume pumps the water out of the hole and into the sewer system.
I installed a mystery switch in my house.
I had a room with three lights on the ceiling all controlled by the same switch and I wanted to install an independently switched ceiling fan in place of the middle light. So I cut a hole in the wall, installed a new switch, and hooked it up to the electric line running in the wall.
That’s when I removed the center light fixture and discovered that they’d actually connected two sets of wires to the one switch, one for the outer two lights and a second for the center light… exactly what I needed after replacing the old single switch with a double switch.
So now I have a switch on the wall of that room that is connected to power but nothing else. I’ve been looking for the perfect switch to put there which will cause the most confusion for the next owner, something like this Panic Button but ideally one that lights up to prove it is connected to power.
My house has a few things:
An exterior light that no one can find wiring for. We think it goes through the attic, but it’s loose cellulose insulation and nobody wants to dig through that when we’re not even sure. The fixture doesn’t get power, but we can’t troubleshoot why without finding the wire.
A high-voltage outlet. The previous owner used this for an arc welder. I repurposed the circuit breaker for my hot tub, so the outlet and wiring are now disconnected. I suppose this isn’t a mystery to me, but it will be to someone someday.
A couple of vents in the garage… it makes no sense to have them there. I thought maybe it was for ventilation, but why? You could just open doors and windows on three sides of the garage and get 30+ sqft of ventilation and not just 2 sqft. Anyway, the imbecile who made them just cut through the sheetrock and siding and then screwed in standard ventilation covers, which means that spiders and the like could not only easily get into the garage, they could easily get between the walls.
My electrical box has the strangest labels. Many of them are just plain wrongly labeled. Some of them are probably labeled that way because they just connect weird things together, like the one that goes to some outlets in the garage and some outlets in the kitchen, even though the kitchen is upstairs and on the other side of the house from the garage. Both the garage and the kitchen have other outlets on different circuits.
It pumps it out? You’d better make sure about just how that works. If there’s a pump, it will likely need maintenance someday so it would help to know just where it is and how it’s wired. If it’s on it’s own circuit breaker and it trips without your knowledge you could end with a bunch of soapy water all over the place.
Label if something like “Govt. Property” or “FBI”, and “Do not remove, disconnect, or interfere with under penalty of law”. Maybe wire it to a circuit that flashes and beeps at random times. 
It sounds like the washing machine is draining into the sump pit. Where it pumps to, who knows…not your optimal installation, for sure.
And I may be mistaken, but I believe in some jurisdictions it’s illegal to discharge a sump pump in to the sanitary sewer.
Assuming that it’s as old as the rest of the house, it was probably legal at least at the time it was built. If it’s not, or it fails in the future… well, that’s the landlord’s responsibility to figure out.
I used to work in a SAGE blockhouse.
On a post that went up through the floor of the Air Surveillance platform was red electrical switch. You know the kind of switch you see in Frankenstein movies.
SAGE had vacuum tube computers and reportedly if the air conditioners went out we had four minutes to pull the switch before the building either caught on fire, or consumed all the oxygen in the building. I thought it didn’t do anything…but never had the courage to pull it.