Both hot wires in a 14/3 run getting power when I only expect one to get power

I've got a strange issue with a lighted ceiling fan in my house.

The wiring in this room appears to be very simple to me. There's one power supply run coming in, one branch to the receptacles, another branch to a switch that leads into the black wire in the 14/3 that leads to the ceiling fan box, and another branch to another switch that leads to the red wire in the 14/3 that leads to the ceiling fan box.

My issue is that if either of the two switches are closed, both the black and the red wires running to the ceiling box are getting power. I don't understand how this is possible without something crazy like damaged insulation allowing current to flow between both hot wires or something.

I tested this by disconnecting the dimmer switch completely and leaving just the regular switch attached to the black wire going to the ceiling. I left the red wire completely disconnected, and closed the switch, and the red wire gets current. I verified at the switch side and the ceiling side.

Here are some pics of the wiring (album link)

I'm very suspicious of the overall wiring here because the switches were left ungrounded, and the wires were wrapped in the wrong direction around the screw terminals.

Any ideas? Thanks for reading

Posted Oct 2, 2021, 5:19 PM UTC

13
amunro11•

My first tip is to not trust that pen tester you're using. First reason, it's been recalled by klein. Second reason, the very principle on how they operate is flawed when you have two conductors extremely close together like in a 14/3 cable. It's likely just inductive coupling if you hooked up everyth. True test, get a multimeter and test to ground from each conductor. This is assuming you've connected everything correctly. The incoming power cable and the one to the receptacles should branch together, the blacks need 2 pigtails coming off of the same marrette connection, one to each switch. The whites ALL connect together. The black and red from the 3 wire, one to each switch. If you've done this, tested with a MULTIMETER, and it's still reading hot on both, take your cable clamps off the boxes, might have tightened them down too much.

7
error__fatalOP•

Wow I did not consider that my method of testing is flawed! I'll test again with my multimeter. Thank you very much.

3
coogie•

Dimmers often have voltage leakage too.

1
[deleted]•

[deleted]

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