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How can I wire a standard light switch to an extension cord? Answered

I am working on a project in which 2 light fixtures are wired up to an outdoor extension cord. I need to wire a light switch like the one pictured below to the extension cord. How can I go about doing this?




Best Answer 5 years ago

Are you thinking of doing an "inline" switch, where you put the box partway along the extension cord, between the plug end and the socket end? That's quite easy.

For outdoor use, get yourself an outdoor-rated single enclosure box (HomeDepot or your favorite local independent hardware store), with good, tight grommets for the breakout holes.

Cut your extension cord through at the point where you want the box (please, make sure it's unplugged first!). Strip about two inches of the outer insulation from the cut ends, then strip 1/2" from each of the three wires inside (black, white, and green).

Thread the two halves into the box from opposite ends, through the grommets. Give yourself at least three inches or more of each half inside the box, then attach the cable clamps to the cords inside the box so they can't pull back through the grommets.

Connect both green wires to the silver (sometimes green painted) grounding screw. Use needlenose pliers to make a loop out of the bare wire, and fit that loop around the screw. You must connect both wires to ground, or your lights will not have a proper grounded connection back to the house.

Twist the two white wires together, and cover them with a terminal cap. For a safe outdoor connection, cover the twisted together wire ends with silicone grease before screwing on the terminal cap. You can also buy caps preloaded with grease for weatherproof installations.

With the needlenose pliers, make loops in the two black wires, as you did with the green (ground) wires above. Attach one black wire to each of the two brass terminal screws, and tighten them completely.

Close up the box, making sure you seat the cover grommet in its slot properly. When you plug in the extension cord, you should be able to turn the lights at the other end on and off.

Awesome, thanks!

For indoor use, do i really need a ground plug? And if I am not going though a box, do I need to cut the white wire?

Thank you!!!

Always ground your circuit properly.

Always go through an enclosure. Those terminals are exposed, and they will be carrying 110VAC at about 10A. That is enough to kill you, or your parent, or your sibling, or your pet. It is also enough to burn down your house.

This is a very easy starter project for learning how to do electrical work. Do it right, and you'll be successful and learn good techniques you can apply to more complex projects.

Do it wrong, and at best you'll short out a circuit and blow a fuse, pissing off your parents. At worst, you will kill or seriously injure someone, or cause several thousand dollars in property damage.


Right. Code requires GFCI on outdoor outlets. Would you put another one on the extension cord itself? I thought it was not recommended to have them daisy-chained, but you have much more expertise in this area than I do.

Older properties might not have ANY GFCI, which is what would worry me. Check. You're right, they aren't supposed to be cascaded, but one should be present.

Over here, we can't mung together standard electrical parts into an externally rated power supply.

By the way, sorry for all that bold at the end of my comment. I missed out on a '</b>' tag :-(

As I noted below, this is an excellent starter project for you to learn about home electrical wiring. Do it right, and you can apply the same skills to replacing or adding light switches in your home, hooking up outlets, dimmer switches, all that good "home repair" stuff.

If it's more important to have something reliable, which you can use indoors or outdoors, you can also buy extension cords with switches built into them. Look for switched extension cord on Google; they cost about ten bucks.