On the weekend the light in our hallway packed it in. Changed bulbs, no difference. Check for power at the light socket, nothing. Change both 3-way switches, no difference.
House is 1930’s vintage, combo of old and new wiring. In the process of checking which wires are which I discover that in the hot box there are there wires; two hot wires and one neutral. What is stranger is that neither of the hot’s read 120 volts, one is 90 volts and the other is 70 something volts. The neutral reads 1 volt…
In the other box, there are three wires, none of which appears to be the common wire.
I am now at a complete loss as to how to fix this, or even how it worked in the first place.
Realizing this is somewhat like trying to perform medical diagnosis over the phone, where should I start looking?
Thanks as always!
David
Replies
I can't do a diagnostic on your wiring from here, but I can tell you what you SHOULD have.
One switch is at the power feed end, the other is at the lamp end. The neutral white from the lamp (and green ground if present) goes back to the power lead end without going to the switches. Between the two switches there are two wires which feed the power, but only one or the other at any one time. It depends on the switch positions as to which of the two leads has power.
The first switch will have a hot lead at one end of the switch and two leads from the other end of the switch casing which are supposed to be connected to the other switch in mirror image.
If the switch at the infeed end is good, you should be able to read nominal line voltage to ground on one of the leads, and when you flip the first switch the power should then be on the other lead. If there is a bad contact in the first switch, the voltage may read lower than nominal in one of them.
At the second switch (the one at the lamp end) the wire all by itself at one end of the case should be the hot lead for the lamp. The other two terminals get the two lines from the first switch and it doesn't matter which one goes where.
That's it. If you can't get it sorted out from that, you probably need somebody to come and actually see what you've got.
Regards,
Don
Thanks Don, if I take the switches out, shouldn't the power feed end have a neutral, a hot and a common wire? It seems I have two hots, neither of which is 120v.
What are you using to measure your voltage and what is it relative to? If using a digital VOM, what you are seeing is "phantom" or induced voltage. If you only have three wires at each switch box, then the hot feed is at the light box, which is also serving as a junction box for the travelers. Check there for loose wires.
Thanks Normel, that is pretty much where I ended up last night as I was thinking about it. I was measuring voltage relative to ground. E.g. one test lead on the wire, other test lead on the ground.
The switch boxes and light box have the following wires
Box 1 = white, black, red, bare copper
Box 2 = 3 blacks, bare copper
Light = white, black
The light gets a thorough check tonight...
Cheers!
David
This is much too confusing for my feeble mind, but here's a couple of questions/observations that may help others. About this red wire that is in one box, but no where else. Either it is a "red" herring, or there is a junction box somewhere in the circuit, where it's connected to a different color wire. Could this light have been on a 4-way switch set-up at one point (ie, light controlled by 3 switches) ? Do you have a blank cover plate anywhere a switch may have been in the past ? Of course, the junction box may now be hidden, in violation of code.
Can you shut off the power, disconnect the wires from everything, and use an ohmmeter to establish which wire is which ? By this I mean you end up with a chart that says, for example, "white wire in box 1 is black wire #3 in box 2. black wire in box 1 is black wire #1 in box 2. red wire in box 1 is black wire #2 in box 2" Then turn power back on and find out which are the incoming hot and neutral. That would at least give us a fighting chance, although all the 3-way switch wiring configurations I know require more conductors than you have ! I know of 5 modern ways to wire a 3 way circuit, depending on where the feed is and where the light is in relation to the switches. (But of course, I never use 4 of the 5 ways. I only wire them one way: the simplest and foolproof way). Since your feed can't be at the light, 3 are eliminated. In both the other configurations, one of the two switches has both a feed and a 3-wire (with ground) cable. Yet you have only 3 conductors in each switchbox. Are you sure you have listed all the wires in the boxes ? (And before it broke, you could definitely turn the light both on and off from either switch, right ?) Maybe the grounds are being used as the neutral ?
No ground at the light, huh ? I take it none of these wires are bundled inside a cable, like Romex or one of its predecessors ? Are they in conduit ?
As I said, I'm not smart enough to figure this out. But if you can answer these questions, I'll bet one of the pro electricians can. (they are lurking now, hoping you will provide more info !)
Do a Google search for 3-way switch diagrams and find one that corresponds to your setup--sounds like your power is coming in at the light. 3-ways can be wired in several configurations depending on the location of the power and how the wire is routed to the switches. If you can't make sense of what you have, be safe and call an electrician.
David, my curiosity is killing me - haven't slept for 2 weeks now. Have you gotten anywhere with your 3 -way switch problem ?
Not a darn thing!. Too many other projects, but this is on my list for tomorrow! Have to keep the priorities straight... boat projects first, house projects second!
OK I spent 2 hours the other morning and managed to get the light to work for .75 seconds!!!
I am at a complete loss as to how this light worked in the first place.
attached is a crude drawing of what I have for wires, continuity and voltage...
O.K. so you peaked my interest. figured with ten messages your problem would have been solved.
According to what I can discern from your postings, the wire count and whatnot are correct. I can't solve the problem, but, if I describe the correct wiring, maybe that will allow you to figure it out from there.
Somewhere along the line you should have this:
Box A - home run or hot wire B, W, Gnd. Also there should be some, I'll say, 14-3 with a B,R,W and Gnd. These wires are connected as follows:
Gnd to other gnds in box, W to W's in box (particularly the W of the 14-3), B to Common terminal on 3-way switch. From the switch you should have B of the 14-3 on one load terminal and R on the other.
Box B - Should have B,R,W, and Gnd from Box A and a B,W, and Gnd to the light. From the 14-3, the B on one load terminal and R on the other of the switch (just as on the switch in Box A). The common should have the B to the light on it. W from 14-3 to W to the light, Gnd to gnd.
To troubleshoot I would disconnect all the wires in each box making sure there is no power to the wires in either switchbox. Find which is the hot wire in Box A. Then, a little trick for those with short tester leads, twist the red and black together at Box A. Then using an ohmmeter, test for continuity on the all black wires (that you said you had in one of your boxes) in box B. This should tell you which pair are the black and red in the second box when you get a zero reading on a pair.
Or you can hook the hot from box A to one of each of the wires in turn and test for power at the second box. This should tell you exactly which wire is which.
Once wires are i.d'd wire as above. hope this helps.
I finally solved the problem with my 3-way switch!!!
After letting the wires and bad karma just hang out for a while, ok so it has been over a month...I decided last night to have another look. I put both switches back in, go to hook up the old fixture and I decide, maybe lets try the new fixture instead.
So I hook up the new fixture and for some reason it works!!!!! Strangest thing... I think it must have been my wife asking me if the fixture was the problem.
Of course being the smart guy I am, I had tested it previously... seemed ok, continuity where there should be and all that good stuff.
Good thing I didn't tear oout walls and wiring...
I guess I'll listen to her a bit sooner next time... :)
Thanks all,
David (basking under the new hall light!)