3-way switch issues

[Matt Harwood]

I know it's a little off-topic, but I know there are some smart electricians watching this forum, so I thought I'd give it a shot.

I'm renovating an old (1927) house with tube-and-peg wiring. There are a pair of 3-way switches that operate the upstairs hall light. Both switches were broken so I replaced them. Now the light works, but it's problematic. If you turn either switch off, the other will not turn the light back on. If the light is on, either switch will turn it off, but you have to use that same switch to turn it back on--the other switch does nothing. It isn't operating like a true 3-way which will turn the lights on and off regardless of the other switch's position.

I've wired and installed many 3-way switches in the past without incident, so I understand how it is supposed to work. Is it possible that the original switches worked differently than modern switches?

I tried various combinations of the wires (which, of course, are all black), and the configuration I have now is the only way the light worked at all. Clearly something is amiss. Unfortunately, there's no way to pull new romex or trace the original wiring because it's embedded in the wall and the switches are quite far apart.

Any suggestions? The switches are too far apart to do a continuity check with a DVOM. And yes, I am using 3-way switches in both positions with all 3 wires connected.

 

[Jay H 237]

It definitely sounds like one of the wires isn't hooked up right causing one switch to act like a master and the other like a slave depending on which one initially turned it on.

Have you pulled the light down and taken a look at the wiring inside the box?

Now having all identical black wires makes it that much more fun!

Which brings me to my next idea,

Even though you said you can't do a continuity check due to the distance you may still be able to isolate and figure out the wires. Do you have a 12 or 24 volt power supply like a doorbell transformer and a 12 or 24 volt test light? With the 110v power off and the wires to the switches and light accessible you can run a spare wire from the test light to the transformer, and then use another piece of wire from the transformer to one end of one of the black wires. Then all you have to do is move the other lead from the test light to each black wire until you find the corresponding one. All you're doing is sending 12 or 24 volts through the wires which shouldn't have any problem with the distance. As you isolate each wire mark it with tape or something and pretty soon you will be able to tell how it's wired and any changes you may have to make.

 

[Luckydevil]

I would just make extensions of wire for the multimeter to do the continuity test. Wrap a piece of wire around each lead and just run it as far as you need it. 50ft spools of wire are dirt cheap at home depot. Just a thought...

 

[TOMWELDS]

You have the "common" (or "pivot") wire on the wrong screw. There are 2 wires that go only from one switch to the other. These are the "travelers". Locate them with your multimeter. The third wire on one switch goes to the light and on the other switch, it's the power feed. (80% of the time..LOL). Dont worry, nothing will short, it just wont work correctly, if the wires arent right.

 

[Matt Harwood]

Thanks for the great replies, guys. I knew I'd get fast and useful information here. I'm going to extend the wires with some romex and do the continuity tests and find the two wires that should go from switch to switch. The upstairs switch definitely has a wire going to the light fixture, so I'm guessing the downstairs switch, which is close to the fuse box, gets the power feed. Once I locate the travelers, I should be all set.

Thanks!

 

[mleichtle]

I did the same thing, only it was a 4 way, replaced 2 switches. I labeled every wire and there was no dought that is was wired correctly, but it did the same thing you described. I futsed with it switching wires, shocked my self a few times then got fed up and put it all back the way it was suppoesed to be, no change. Then a few days later, it magically started working. Still a mystery. Its like the switches had to be broken in.

 

[ranger_dood]

So.. you're leaving the tube-and-peg wiring in place? I would not suggest that at all, but I guess that's up to you. That wiring insulation is probably dryrotted all over the place...

I'm trying to get my uncle to have someone replace the wiring in his house... His house was built before there was electricity, so when they did run wires, they cut holes in the floor all over the place to pull the wire. So it really wouldn't be too hard for him to get someone to run all new romex. For him, all the wires take the easiest path to the basement, since they were run after the walls were closed...

He's still running the old steam radiators for heat, too :x

 

[TOMWELDS]

The best thing you can do with the knob and tube wiring (other than replace it) is put a GFI breaker on that circuit. That's assuming there are breakers and not fuses. If you're renovating...dump that circuit and put in new.