01:48PM | 03/16/03
Member Since: 03/15/03
2 lifetime posts

My wife and I are installing new track lighting in our house in a room that has an outlet controlled by two three-way switches. In the process of testing the switches with a voltmeter, we discovered two things:
First, the three way switches don't appear to be wired up correctly. If they are both off, we can turn the plug on with either one, but if one is in the ON position, the other switch does nothing (I know, this is a common wiring goof in three-way switches, but we have some pretty good guides that show exactly how to wire them up, and they are still not working. See the details below.)

Second, and of a greater concern to us, when the outlet is OFF (a lamp plugged into it turns off with the switch) there is still power going through the outlet... about 40 volts on the voltmeter when touching the two screws on opposite sides of the outlet.

To make things a little more complicated (and more crowded in the outlet box) the original owner had the bottom plug on the outlet wired for continuous power and the upper plug wired up so as to be controlled by the three-way switches. We have decided to make the entire outlet controlled by the switches (no continuous power.)

We have 4 sets of wires coming into the outlet box. Two are the three-wire types (black, white, red and the ground) coming from the two three way switches. The other two are the two-wire type and am pretty sure one is the source and the other just a feed down to another plug further down the wall. Both three-way switches have ONLY the black, white, red wires coming in (with ground on the box) and red is connected to the common, black and white two the other two brass screws (same way on each switch.)

My wife and I spent an hour going through wiring but still couldn't get the three-way switches to work properly. Here is what we have in the outlet box:
- the two red wires from the switches are wired together
- the two white wires from the switches are wired together
- black wires from switch 1 and power source wired together
- white wires from power source and outlet wired together
- black wires from outlet and switch 2 wired together.

The 40 volt mystery led me to check the other rooms in our house that have outlets controlled by switches (some three-way, some not.) One other room showed the same symptoms at an outlet controlled by a switch (but not a three-way.) Best I can tell, it is on a separate circuit.

We purchased our house about 3 years ago (it was built in 1979) and have been slowly replacing all the old switches and outlets as we go. We're no strangers to do-it-yourself projects, but we're stumped as to what is going on with our wiring.

Any suggestions?

Ps. just remembered something that might be tied to this... maybe... we have one outlet in our living room that always gives a little spark when you plug something into (kind of like if you have the vacuum cleaner switched on and THEN go to plug it in.) Our little plug-in tester says every thing is fine. We have a surge suppressor strip plugged into now, which did not get rid of the cause of the problem, but did fix the symptoms (no sparks when we plug things into the power strip.)

[This message has been edited by dvonderw (edited March 16, 2003).]

[This message has been edited by dvonderw (edited March 16, 2003).]

Electric Eagle

03:40PM | 03/17/03
Member Since: 03/01/03
6 lifetime posts
First, on your 3 way switches black is almost always common and from what you described the black is common for your switches also. Change that and they should work. As for stray voltage, that's tough to diagnose over the 'net, but may be a false reading on your meter or could be a problem. Hope this helps.


02:51AM | 03/18/03
Member Since: 09/17/02
524 lifetime posts
If the outlet was previously 1/2 switched then you need to change the outlet. The tab on the gold(hot) should have been removed. It needs to be there or only 1/2 the outlet will work unless you install a pigtail to both gold screws.


02:45PM | 03/18/03
Member Since: 03/15/03
2 lifetime posts
Thanks Electric Eagle! You were right on the money... made the black the common on the switches and the three-ways worked properly. For some reason, our guide (freebie that we picked up from Ace Hardware store years ago) had everything right except it indicated that the RED was to be the common.

Also, regarding the mysterious voltage still present with the switch off... I did some more troubleshooting tonight. Turns out that if I have the RadioShack plug-in tester (three lights... two greens = all is good) in the outlet but pulled out so I can touch the two terminal spades (or whatever you call them... not the ground) I get a reading of about 40-50 volts. If I plug in any old lamp (just the two spades, not ground) I get a reading of zero.

The plug-in tester says at 125 V it uses 0.3 W... so I'm guessing it has pretty low resistance... would this have anything to do with me seeing the 40-50 V readings on my voltmeter? By the way, I tested my voltmeter on some other circuits and it seems to be okay. I did try plugging in something besides the tester that had a ground on the plug... when I plugged in a power strip and read the voltage by again touching the two spades, I got about 1.5 volt reading.

I'm concerned that I have a partial short somewhere in my wiring or something... the previous owner did some ad-hoc wiring additions and we're still finding & fixing them...

Maybe my voltmeter is shot at the low end of the range... I'll pick up another one this week and see what I get with it.

Thanks again for the help!

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