# How to Figure Out Light Switches That Do Nothing



## Kenny1948 (Jul 12, 2017)

I had one of these mystery switches in my Mom's house. Was never able to figure out what it was connected to. It remained live, no matter what circuit breakers were turned off. We were never able to figure it out. It seemingly controlled nothing in the house.


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## vandamme (Aug 19, 2016)

My daughter bought a 1930's era house in Boston, and I spent a few hours on the inscrutable wiring. It helps to make a schematic/wiring diagram and have a multimeter. They had a couple 4-way switches that died, ungrounded boxes, capped-off and plastered over outlets, and other mysteries.


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## Steve3 (Mar 23, 2018)

Rather than run back and forth between the switch and outlets I ran to the dollar store and bought some cheap night lights. For under $10 it allowed me test all the outlets in the room at once.


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## Gregwashere (Jun 23, 2012)

Professional electrician here...I hope this is helpful and can save some folks some money.,..
1). The language of the first idea suggests turning the switch on and off to check each receptacle or other location. Instead of starting with the switch "on", turn it OFF. THEN go around with a lamp or tester (for $6, you can get a 3-prong tester at Home depot that will also check for grounding and reversed polarity as soon as you plug it in) to check each socket (top and bottom) to see if any of them DON'T work. If you find one that doesn't work, go back and turn the switch on. If the lamp turns on , you have your answer. If not, turn the switch back off and continue looking for something that doesn't work.
Further investigating:
1). In older homes, look for a 4"(maybe larger) round(ish) patch in the ceiling plaster -it may be that there was once a chandelier that was removed and the hole was patched over.
2). Check your outdoor lights at night. Turn the mystery switch ON. Do the lights all come on? Make sure that you at least try putting new light bulbs (*cough* Upgrade to LEDs *cough*) into any sockets that don't come on. Once everything is on, go turn the mystery switch OFF. If you lose power to one of the lights, you have an answer ...amazing how many of these I have found! 
3). If you take the cover plate off the switch and there are 3 wires (+ maybe) a ground wire, keep in mind that this may be a 3-way switch that was mis-wired. Admittedly, this is probably beyond the scope of the article.

"Testing for electricity" ...Proximity testers (ALL of them -and I have owned many) are virtually useless in a switch or receptacle box unless there is only one switch or receptacle in there. If there are multiple devices, you'll have to pull them out of the wallbox to separate the individual wires enough to get an accurate reading. Any other electricity within 4" may give a false positive because these instruments are notoriously flakey. I don't even bother carrying one of these in my pouch.
In addition, even if you get a positive reading on a switch, you really need to know whether the electricity is passing through the switch ...so you'll have to take the device out of the wallbox to test BOTH wires that are attached to the switch (or, if it's a 3-way switch, all 3 -sorry for the extra detail). Though less safe than a proximity tester, it is much better to use a contact tester from an electrical supply store (or a VOM if you can).

"Tracing the wiring" Do NOT buy a $100 circuit tracer. Again: useless for any certain, confirmable trouble shooting involving tracing wires through walls. I have a $1,200 circuit tracer and it is "acceptable". I don't a single electrician who doesn't think this baby is top of the line and I agree. Is it worth it for a DIYer to buy one of these? NO. It's cheaper to hire an electrician.
...And do you know what we will do after checking the above information? We will NOT trace the wire. We will disconnect it. Because that switch did "nothing" before, we will assume that the wire goes to a buried junction box and we will simply kill it. *IF* in the future, there is another problem, maybe we'll come back, reconnect the wire ...and if that works, we'll probably smile sheepishly and -if we are decent human beings- apologise for not catching it the first time and leave without a payment.
If you are handy, turn off the power, disconnect the switch, cap the wires. Don't trace the wire ...it's 99% a waste of time. Be happy you saved yourself some time & money, and celebrate by spending some quality time with someone you love.


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## Cenzo22 (Mar 30, 2008)

Some years ago I made a diagram of every outlet,fixture,switch.etc. for each floor of my home and numbered them to the circuit breaker number. I then know what circuit breaker controls what outlet, switch, etc. Since I have a generator with a Gen Tran switch, I colored in red every outlet, fixture, etc. when the generator is running. The generator runs important circuits such as refrigerator, freezer, boiler, TV, microwave, and some lights. It is a two person job with phone communication to make the job easier.


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## Dokota99 (Jan 12, 2011)

If you have a mystery switch that remain live after turning of the breakers. Then you should turn of the Service Disconnect breaker. Usually located above the branch circuit breaker. Or outside below the Power company meter socket. Enclose in gray weatherproof book. Turn this one off. The switch should be off. I talking a single family home. If you live in a house converted into apartments, you need to contact your Land Loard.


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## chuck_d (Mar 23, 2018)

I have a switch in my bedroom that controls a light in Germany.


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## Sparkie1 (Mar 23, 2018)

Also they can look in basement under switch for a junction box with only one romex in it. Found these to be for a front door post light that was never installed.


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## harleyron (Mar 24, 2018)

I'd like to have A mystery switch that controlled my neighbors stereo!!


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## Alen (Mar 24, 2018)

I also found a seemingly dead circuit breaker. After my Dad passed, checking his home, I forgot he added a circuit to the attic to add an outlet and light. Thats why he kept it off until needed.


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## mzaborsk (Nov 15, 2016)

People are simply amazing on how they spend their time....licence electrican


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