Light switch polarity question.

Old 12-28-05, 06:44 PM
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Light switch polarity question.

I have a new curio cabinet with 120V 40W light fixture. I had no outlet nearby so I tapped into a nearby 3-way wall light switch to power the curio light by hard wiring an extention cord and running it out behind a small cut-away in the switchplate (The wall switch powers two hallway lights).

I did the following: 1) Cut off the male end of an extention cord and prepared the wire ends to tie into the switch. 2) I attached the side of the extention cord wire that came from the side that the wide male prong to the the terminal screw that is always powered on the wall switch. I understand the wide vs. narrow male prongs are related to polarity and I thought the wire from the wide prong should go to the always powered terminal on the wall switch. Is this right, wrong, or does it matter if the wire is from the wide prong or narrow prong side? 3) I attached the other extention cord wire to the two White (neutral) wires that were connecte together in the switch box.

I turned the power back on, and then I tested my newly powered extention cord by plugging in the cord which powers the curio light into the extention. The cord for the curio has an in-line roller type switch. Rolling the switch on and off provided power to the curio light with no apparent problem. The curio light turned on and off with no problem. The 3-way wall switch also continued to function normally as well.

After several minutes of working on other parts of the curio and occasionally turning the curio light off and on, I went to turn the light back on and it no longer worked. I checked and power was no longer feeding through my extention. I tested it with other lights and a volt meter and found it no longer had power.

I am wondering the following: 1) Did I wire my extension backwards and if so, did the reversed polarity cause the extention to fail. If so, I assume I should mount a new cord with the wires switched on the new one, correct?

I have since checked the wall switch with a multi meter and it seems that the terminal that I had screwed the extention wire to (the terminal that had power all the time) no longer has power...either with the wall light switch in the on or off position.

I am adding another note, because I just found that the issue is related to using the switches at both ends of the hall. Apparently when the other switch was moved to its other position, it cut the power to the terminal that I thought was always powered on the switch I had connected my extention to. I need to find a wire that is always powered no matter what position either switch is in... I will work on this more tomorrow...

I would still appreciate any comments and suggestions. Thank You

Last edited by DELOREAN; 12-28-05 at 09:08 PM. Reason: Adding information
Old 12-28-05, 07:34 PM
Join Date: Sep 2002
Location: welland ontario
Posts: 8,341
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I only read the first paragraph of your post. Remove it now. It is dangerous and not anywhere near a code installation. Plus most of thime you can't tap into a switch for power but I didn't read that far into your post.

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