Tracing a light switch that seems to do nothing

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  #1  
Old 11-12-15, 03:19 PM
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Tracing a light switch that seems to do nothing

Is there a device that can trace what a light switch we seems to do nothing?

I've read prior similar threads - The light switches in question DO NOT control any of the receptacles in the room - top or bottom. There ARE live wires attached to the switches. The breakers that control these switches control other lights as well so it doesn't narrow it down. Any suggestions? Thanks

The house is fairly old (90 years). There is signs of abandoned/non-working wiring throughout
 
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Old 11-12-15, 03:38 PM
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There is a wire tracer device, commonly called a fox and hound, that can trace wiring. The inexpensive ones require the circuit be de-energized, or you can pay a lot more for one that works when the circuit is hot.

It will help you trace the wiring on that circuit...but no guarantee it will be enough to solve the mystery. It can't distinguish between wiring coming in to the switch and wiring going out, it will respond to all of it, but usually it's enough information to sort things out.

Do you have attic and basement access above or below that would let you physically trace the wires?

Have you opened the outlet boxes in the room to see if there are any abandoned cables that might have controlled an outlet in the past?
 
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Old 11-12-15, 03:58 PM
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Short of removing all the plaster from the walls, there is no way to follow the wire that is being switched by the do nothing switch (DNS). If you know the breaker that removes power from the DNS, open breaker, remove switch, remove and wire nut each wire removed from DNS (should only be 2 wires ). Get a new cover plate for the switch box and turn the power back on. Good luck.
 
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Old 11-12-15, 05:48 PM
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Short of removing all the plaster from the walls, there is no way to follow the wire that is being switched by the do nothing switch (DNS).
Installed wiring can be traced without removing the wall finish. Post #2 describes one method. Another is to ensure the power is off and intentionally short the wires together. Then wires are checked for continuity around the room.
 
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Old 11-12-15, 06:26 PM
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If the house is 90 years old.... the wiring may be metal clad like BX.
You cannot tone thru metal clad cable to locate the cable in the wall.

You can use a toner at all the junctions boxes as long as the power is off.
 
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