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I just finished tearing my office down to the studs, insulating, and then having drywall installed. The crew did the drywall install today. I have a light switch which is a dimmer that powers 4 "cans" AKA recessed lights. After the drywall install I flipped the switch and the lights came on with a loud POP noise. I turned the switch off and then on again. This time nothing happened for about 5 seconds and then the lights came on. I turned the light off and on about 50 more times and now it always works but there's a low hum that did not exist before. I suspect an electrical short situation was created during the drywall install but I'm not much of an electrician. Where should I look for problems and how should I solve this? Will my house possibly burn down?

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This sounds like a rather dangerous situation. The drywall installers no doubt did not install metal straps on the studs wherever an electrical wire crossed through the stud. Most likely a drywall screw or nail has gone into the stud and entered a wire that crossed the stud in the same place.

The fix for this may require a professional electrician unless you are pretty familiar with electrical wiring work. It will be necessary to cut the power to the circuits and open all the applicable electrical boxes and disconnect the various lights, switches and power feed wires. Then shorts checks can be made using an appropriate ohm meter for all the wires in the area between the boxes.

Once the short is located it will likely be necessary to remove the drywall in that area to replace the wire.

Do not leave this problem go. It sounds like you have a medium resistance short in some wire/stud crossing. I say medium because you did not mention that it is tripping a breaker. The resistive short can produce a lot of heat and could definitely lead to a fire in your wall or ceiling.

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If the drywall screws are still exposed, you could turn the switch on and go around touching all the screws. The screw that makes your finger tingle, is the one that's through the wiring. (WARNING: This is for entertainment purposes only. DO NOT do this.) –  Tester101 Jun 4 at 11:08
    
Well the switch wires run directly up the wall by the switch. I noted the wiring prior to the drywall. Would it then be safe to say that the short has to be in the vertical area above the switch? –  Haney Jun 4 at 14:02
    
No. The wire could be compromised in the run to any of the cans, or even in a line heading toward the switch. –  bib Jun 4 at 14:22
    
The cans are in the roof which was not drywalled. Only the walls were. So I assume the damage is at the switch where it runs up the wall? –  Haney Jun 4 at 15:14
    
@Tester101 What you can do instead is use a multimeter in AC volts mode (20VAC range or lower), and find the one that has the highest voltage when you touch one probe to it, with the other not touching anything. ( you can sometimes also remove the other probe from the multimeter for extra safety ) This works by capacitive coupling the multimeters internal wiring of other probe to you. So it is quite safe up-to the rating of the multimeter. The actual value will change with different multimeters. It also won't work with some cheap ones. –  Brad Gilbert Jun 4 at 15:34
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