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Do I have a wiring problem?

pendragon1998

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Mar 24, 2012
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3,733
Location
NE Georgia
Our bathroom has a two switch wall panel that controls the fan and the light over the sink. Today, when I switched on the bathroom light, I heard a sizzling from the wall switch, and the light was flickering. I figured it was likely a bad switch. They used the cheapest builder grade **** they could find for this house, which is a two-section modular home.

I bought two single pole switches and replaced both switches, being careful to swap each wire over where it was on the corresponding original switch. The stripped areas on the original wires were a tad longer than they needed to be, so I even nipped a 1/8" off the bare ends so there wouldn't be any bare wire protruding (probably overkill).

When I flipped the breaker back on, it immediately tripped. I removed both switches again, thinking I'd screwed up somehow. I checked both switches for resistance before reinstalling them, and they were working just as they should. I reinstalled the switches. Once reinstalled, I again tested resistance in the on and off postions. One switch was working correctly, but the other switch only has 56 ohms of resistance when it's switched off. This time, however, the breaker didn't trip.

Am I correct in thinking I probably have an intermittent short in the wiring? We previously had some wiring with abraded insulation from where the wires crossed over from the breaker box side of the house to the other module that holds the water heater, so it wouldn't surprise me. If it's the wiring, I'll call in an electrician.
 
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justsam

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Aug 20, 2010
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Penngrove, California
Not sure how you are measuring the resistance of the circuit. You may well be looking at the internal resistance of a light bulb or fan motor, which would be OK.
 
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Mustang51js

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Jan 24, 2014
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Haskell nj
How many times did you try to turn breaker back on before retiring switches. Does the light work now and what type of boxes did they use, you may have a nicked wire from sheet rocker that was touching something.
 
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pendragon1998

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Joined
Mar 24, 2012
Messages
3,733
Location
NE Georgia
I was measuring the resistance with my HF multimeter set at 200 ohms, across the two screws on the side of the switches (switched 'off'). The switch going to the fan was the one with reading 56 ohms while switched off. The light was reading at least 200 (I didn't try higher ranges). I tried the breaker 3 or 4 times and it tripped almost immediately. Aftet pulling out the switches and reinserting them, which moved the wires around a little, it didnt trip. Everything works now. Thats what makes me think a bare spot on a wire might be shorting when it hits another just right.
 
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