Ask Me Help Desk - Can I replace a light switch with an outlet?

I am not an electrician, but I have had some luck doing smaller electrical work around my house, and I need some advice.

I have a house built around 1936. Five of the rooms have central lighting. Four other rooms might have had overhead lights at some point, but if so those lights have been removed, the holes patched up, and the ceilings repainted. (The reason I think so is that those four rooms have light switches that seem to control nothing -- no lights, no outlets.)

Here is my primary question

In the master bedroom, I have one light switch that seems to control nothing. I want to replace that switch with an outlet. Can I do this? What are the pros, cons, and dangers of making this change?

Here are some details to help you answer my question: I removed the switch to see what kind of wires are back there. There are three wires, all encased in black insulation; two of the wires are twisted together and the third remains separate. I used a voltage tester and I am unsure as to whether any power actually goes through these wires when the fuses are plugged in (however, power MUST go through them because if I untwist the two wires mentioned above, no outlets work in the entire room -- right?)

BTW Are the two wires twisted together the hot? Is the third, separate wire the neutral?

Thanks for everything...
Kathleen

Well you using the right words, hot, neutral, etc. and you using a voltage tester. And with the tester you cannot find 120 volts? As you seen to already know you need both a hot and a neutrla to connect to an outlet. A switch box may or may not have a neutral in it depending on how the circuit was cabled.

You don't say which wires were connected to the switch, or if at all.

The two wires spliced may have been connected to the switch, and are connected to jump out the switch, so there is a hot and switch leg. What the third wire is for, can be a spare, a neutral, who knows.

Using a tester, you can, if the cable is metal BX, and is grounded, touch one lead to the box and the other to each wire to find which wire is hot. If one is hot , and you get no reading on the others, and you do not get 120 volts across the hot and either of the two wires, then all you have is a hot, switch legs, and no neutral.

If you knew where the other end of this 3 wire cable was, you could re-splice it so you can deliver a hot and a neutral to the switch box, and install the outlet.

Since the old ceiling lights are now covered, and if there is no attic to gain access to the other end, then I see no hope.

Are you sure there was a ceiling outlet? The switch may have controlled an outlet in the room, so you may find the other end of this cable in any one of the outlets in that room.

The wires twisted together as well as the third, independent wire, were all connected to the old switch, one on the top right of the switch, the other on the bottom left. (I don't remember whether the wires twisted together were connected to the top right or the bottom left.) I know that newer switches now have the silver and the copper screws to help people connect black and white wires -- this old switch only has two screws and both are silver colored. There's nothing to indicate where hot wires or neutral wires go.

The cable from which all three wires protrude is not metal BX. It consists of the three black insulated copper wires all wrapped by tan/beige rubber/plastic insulation. There's paper, too. The box is metal.

So... I guess what I also want to know is this. I read up on old questions regarding swtiching a switch to an outlet. Many people say that making this change is against code. I don't want to burn the house down! Am I asking for trouble?

Thanks!!
K

Quote:

Originally Posted by teachermom

The wires twisted together as well as the third, independent wire, were all connected to the old switch, one on the top right of the switch, the other on the bottom left. (I don't remember whether the wires twisted together were connected to the top right or the bottom left.)

So two wires twisted were on one screw, and the lone wire was on the other?

Quote:

Originally Posted by teachermom

I know that newer switches now have the silver and the copper screws to help people connect black and white wires -- this old switch only has two screws and both are silver colored. There's nothing to indicate where hot wires or neutral wires go.

Since when do switches have brass and silver screws? I am not aware of that, where did you learn this? Switches do not need or use a neutral, handle only hot wires, switching the neutral is no longer allowed, so all of the thousands I have seen only have brass screws.

Some of the older switches may have had silver screws, but the threaded plate were usually brass, and back then things were not so much standard, as they are now.

Quote:

Originally Posted by teachermom

The cable from which all three wires protrude is not metal BX. It consists of the three black insulated copper wires all wrapped by tan/beige rubber/plastic insulation. There's paper, too. The box is metal.

Sounds like the older nonmetallic cable, the first or older version of Romex, which did not have an equipment ground wire, so the box is not grounded.

Quote:

Originally Posted by teachermom

So...I guess what I also want to know is this. I read up on old questions regarding swtiching a switch to an outlet. Many people say that making this change is against code. I don't want to burn the house down! Am I asking for trouble?

Who says switching outlets is against code? Never was and still is allowed to switch an outlet. This is very popular in new homes to switch an outlet(s) to not have ceiling light fixtures. I have done this years ago, and still do this. Those who say switching an outlet is against code, if in the USA, need to show or prove this.

I just don't think you have a hot and a neutral in the switch box to install the outlet. Your only recourse will be to find the other end to see if you can re-splice the feed end to send a hot and a neutral to this switch box.