Wire Short?!? - Electrical - DIY Chatroom Home Improvement Forum

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Old 07-12-2013, 02:54 AM   #1
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Wire Short?!?

I completely gutted a bathroom, and installed new everything, including a new fan. The old fan was just a fan, but the new one also has a light. To handle the fan and light separately, I ran a 3-wire from the new junction box to the fan. The fan runs fine, but when I turn on the light, the circuit breaker trips, and I get a faint wiff that something burned.

The wiring at the fan looks fine, although I can't see much of the fan's internal wiring.

Is there any way to test the wire itself to see if it's shorting out somewhere along the cable?

Thanks for your help,


P.S. - I should add that the cable runs along metal studs (that's what was used for the walls of the bathroom).


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Old 07-12-2013, 06:33 AM   #2
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Did you miswire the wall switch for the light? If you connected it to a neutral, and then switched it on, you may have created a dead short condition....



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Old 07-12-2013, 06:47 AM   #3
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you said you ran a 3 wire from a new junction box ,what junction box is this? You should have a 3 wire from the switch.
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Old 07-12-2013, 11:36 AM   #4
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Smoke smell is not a good sign. Check the switch and the connections inside the fan/light combo.
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Old 07-12-2013, 11:51 AM   #5
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Where is the incomming power goes to ?

That will make the differnce on how it connected.

Double check the connection at both fan unit et switch box to make sure it is not cross connected somewhere at all.

The answer will be based on NEC ( National Electrical code ) or CEC ( Cananda Electrical code ) or ECF ( Electrique Code France )
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Old 07-12-2013, 01:45 PM   #6
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OK, let me provide some additional detail.

This is part of a larger project. Since I had a number of changes to the condo's wiring (including several new circuits), I pulled an electrical permit.

With regards to this particular aspect of the project, the bathroom had been wired in with a bedroom. Since this is not current code, I ran a new 20 amp circuit to the bathroom (note: the bathroom is the only room on that circuit). The feed goes first to an outlet box (for a GFCI outlet) and then to a box which will contain three switches. One switch will be for the light over the sink (it has its own cable). The second and third switches are to separately control the fan and light in the ceiling fan unit. For this, I ran a 3-wire.

After finishing all the rough-in wiring, I called for an inspection. The inspector passed the rough-in, although he didn't inspect all that hard.

Right now, I'm trying to get the fan light working so that I can paint the bathroom walls. Given that I still have to paint, I decided not to install the GFCI, but simply wire nut together the cables in the outlet box. This gives me power to the switch box. The sink light connection works. The fan motor turns on and moves air. The fan light trips the circuit breaker.

With regards to the neutrals (white), all of these are wired to each other -- both inside the boxes and in the fan unit. Nowhere am I running white as black.

I've checked my wiring at the fan against the instructions included with the fan. It appears correct.

Hope the above helps ...

If you were faced with this situation, how would you go about checking it out? Is there any way to check the wires in 3-wire (or any cable for that matter) to see if one of them is shorted?


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Old 07-12-2013, 01:57 PM   #7
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-Turn off the breaker
-Undo the splice on the hot wires
-Check for continuity from each individual hot wire to ground
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Old 07-12-2013, 02:02 PM   #8
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Richard.... Yes... there is a relatively easy way... especially with all your boxes presently open.

Are you familiar with a multi-meter, and just get an extension cord (a long jumper... I just carry a long lamp cord) and break your splices and check for any x-continuity between your hot and your neutral/ and ground.

A multi-meter is 10 bucks at Wallmart... but you can do it with a 9volt battery and a 9 volt light..... it's just more wire/messy.

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Old 07-14-2013, 03:09 PM   #9
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Sorry to take awhile to get back to this thread.

I sense what you're telling me to do, but the actual specifics are just beyond my ken ...

I take it I could do this with a multimeter (the easy way if I had a multimeter), or with lamp cord/battery/bulb if I don't.

I like the idea of picking up a multimeter. I've sensed they could be useful, but haven't had an excuse to go get one. My hesitation is that I don't know what I should be looking for in a multimeter, or who makes a reasonably good quality one. You look in the stores and online, and it seems as if everyone and their brother makes several. If you guys have any suggestions, I'm open to them. Heck, I think I'll start a thread in the Tools section (Multimeter Recommendations).

If I go the lamp cord/battery/bulb route, how exactly do I do that? I sense that I'm supposed to use these components to construct a testing circuit, but just how do I do that?

Finally, with regards to materials, lamp cord I've got. What kind of bulb do I use: flashlight? Regular bulb? And lastly, while I think I can scrounge up a 9v battery, does it need to be this specifically?

Thanks for your help!



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