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I am trying to replace an outside motion detector light fixture that was removed before I bought the house and the only things left were the plastic base in the eave and electrical taped wires shoved through it.

I pulled everything apart and have 2 separate 14/2 wires and neither is always live from the panel according to my non-contact voltage tester, both are switched and only live when flipped on at the switch inside the house.

Well I tried wiring up 1 set of black and white wires and just taping off the other to see if that would work but no luck. I'm not sure why there would be 2 sets of switched black and white wires. I'm assuming I'm wiring something wrong and its not a bad fixture but that's always a possibility.

Anyone seen this configuration before and have any ideas?

  • Do you have a multimeter or voltmeter? – Tester101 Oct 27 '15 at 12:44
  • I do have a multimeter but was unsure of what to check – user2816012 Oct 27 '15 at 13:00
  • One switch energizing both 14/2 pairs is a bit curious. Are you sure this is happening? Use the multimeter to check A/C voltage on each pair. The non-contact device could be giving "better safe than sorry" results. – JPhi1618 Oct 27 '15 at 13:06
  • Use the multimeter to measure the voltage between each of the black/white pairs (black -> white, black -> white), with the switch in each position. If there's a grounding conductor, measure the voltage between ground and each of the conductors, with the switch in each position. This should give you more accurate results than a non-contact tester. NOTE: You'll be measuring AC volts, so the meter should be set to VAC. – Tester101 Oct 27 '15 at 15:17
  • Unless it is the gray-sheathed exterior type, romex (NM-B) does not belong in an outside light fixture, which is a wet location. – Ecnerwal Oct 27 '15 at 18:52
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Could this be part of a 3 way switch, another switch in a different location? that could be the reason for 2 sets and why not working with 1 set removed (wires) one easy way to tell: pull the switch if it has 3 electrical connections (possibly a 4th as a ground) it is a 3 way then we would need to see what the voltages are with the different positions to help hook them up

  • Unfortunately not. Before starting the outside portion of this project I replaced the light switch itself and the only thing in the box were the 2 wires connected to the old switch and the ground wire. – user2816012 Oct 27 '15 at 18:53
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Non-contact testers are not the most reliable as induction from a nearby hot wire can bleed off causing a false reading.

It is also possible, though not as common, to get false readings even when using expensive digital multi-meters because of a bad smart switch.

Also, a bad tap in a junction box could very well be letting just enough voltage to pass, giving a false reading. Then when a load is drawn, the bad tap opens up cutting off the voltage.

These types of problems usually requires some expertise in troubleshooting, and often the electrician may just end up pulling a entire new circuit.

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I replaced the light switch itself and the only thing in the box were the 2 wires connected to the old switch and the ground wire

Since there is only 2 wires in the switch box, that means the switch is at the end of the line. So to fix this light, you just need to wire it like this diagram:

enter image description here

To figure out which cable coming in to the light box is from the breaker and which is from the switch, hook the light directly to one cable and ignore the other cable. Turn the breaker on. If the light comes on, then that cable is coming from the breaker.

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