Expert: Bob Thompson - 2/21/2006

Question
Hello,
I figured replacing a single pole switch would be a straightforward process, but the wires in my switchboxes are all black.  To make things more complicated, the old switches only have two connection points, but are connected to three wires - in one case there are wires in both the push hole and the screw terminal; in the other case the two wires are both on the screw terminal.

A friend of mine suggested that the singleton wires are the hot ones, but even if he's right, I still don't know how to tell which of the remaining two is neutral and which is the ground.

The only thing that seems to differentiate the wires is that, for each switch, there are two bundles that come out of the upper left and upper right; and for each box regardless of whether it has one or two switches, there is a bundle of wires coming out of the lower center of the box.  I can also see a bundle of obviously bare wire in the boxes, but haven't been able to tell with a flashlight where it comes from or where it goes yet.

The new switches I bought say they have to be grounded.

Thanks in advance,
Kat

Answer
Really? All the wires are black? I'd like to see what kind of conductors your house is wired with.

You may have to call an electrician, but let me offer this: You said that some wires were obviously bare...those are the ground wires. They would all join together, and possibly have a 'pigtail' with which you ground your switch. There should be a green colored screw.

You probably have one wire that enters your box that has power on it all the time. With a voltmeter, place one lead on the bare wires and with the other lead, touch each wire, one at a time. All wires need to be isolated and hanging in free air. Once you've located this hot wire, mark it somehow. Now with one lead of your ohmmeter on the bare wires, use the other lead and touch every other wire, one at a time. Some wires you should measure zero resistance. These are the neutrals. Some wires should measure some resistance. These most likely are switch legs and what you're reading, is the load on the other end, such as a 60 watt lamp. All the neutrals will join together.

The hot wire previously identified will go on one side of the switch, the other wires that showed some resistance will go on the other side of the switch. Now for a little fine tuning. When you turn the switch on, you may notice that two things are on, instead of one. By that I mean, you may have a light, on a separate switch, that doesn't work, unless the first switch is on. If that is so, the wire feeding this second switch, is connected to the load side of the switch you're working on, rather than the line side, which has the hot wire you discovered. You need to identify this wire, and move it to the switch's other terminal.

I don't know how mechanically inclined you are, but this procedure would be handled much faster, probably, by someone qualified. A homeowner could do it however.