3-way light in old house blows bulbs

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Old 12-22-18, 09:57 AM
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3-way light in old house blows bulbs

I'm not sure if this is a "lighting" thing or an electrical thing, but...

We have an old house. It has a light at the top of the stairs to the second floor with switches at the top and bottom. When we put in a bulb, and turn on one of the switches it works. BUT, depending on the position of the two switches – I’m not sure exactly what the position is for each switch - the light gets VERY bright and quickly (seconds or a few minutes) burns out the bulb.

All the wiring to the light fixture, and the switch at the bottom of the stairs are the older wire with the heavy black braided covering.

The switch at the BOTTOM of the stairs has 3 wires – ALL black. There is a wire in the top left, wire in the top right, and wire in the bottom right.

The switch at the top of the stairs has three wires also: bottom left is black, bottom right is white, top right is green. I don’t THINK the colors mean anything.

I disconnected the switch at the bottom of the steps and with all the wires disconnected the light doesn’t come on at all regardless of switch position at the TOP of the stairs. If I connect the bottom switch bottom right and top left wires, the switch at the top of the stairs works, though “on” is down rather than up.

So that’s where things are at the moment. The top switch works…

This morning I took a DVM and did some testing (since all the wires to the bottom switch are black, and the one’s to the top switch don’t seem to be colored meaningfully) to try and figure out what connects to what. I connected a LONG piece of wire to a known ground and looked at what’s connected to what as best as I can.

I disconnected the three wires from the bottom switch so I was only looking at things that connect at the top switch. With my wire connected to a known ground, I got:
Top switch, bottom right (white) 120V
Top switch in up position, top right (green) 120V
Bottom switch, bottom right (black) 120v
The LIGHT fixture has 2 wires, a short one and a long one. Both black. With the top switch DOWN, the SHORT wire has 120V. The fixture was connected with the black wire to the bulb on the short wire and the white wire to the “long” wire.

Then, with the power off I started looking at continuity between wires and got:

Bottom switch, top right (black) wire connects to the top switch, bottom left(black) REGARDLESS of the switch position of the top switch. With the top switch DOWN, the bottom switch, top right wire connects to BOTH the top switch, bottom left (black) and top right (green) (I presume when I flip the switch it’s connecting the bottom left (black) to the top right (green)

The bottom switch, bottom right connects to the top switch, bottom right (white). These are the two wires that are 120V when the power is on so I presume they’re connected SOMEWHERE in some wall, crawl space, attic or other area I’m not going into.

The bottom switch, top right wire also goes to the LONG wire in the light fixture (this is the wire in the light that does NOT have power on it when the top switch is on (down). When I took the fixture down, the white wire to the bulb was on this “long” wire…

The bottom switch top LEFT wire connects to the SHORT wire in the light fixture – the one that has power on it when the power is on… I’m guessing that since to have just the top switch work to turn the light on and off I have the bottom right and top left wires connected, the fixture is getting 120V all the time, and flipping the TOP switch just provides a return path?

I know there should be a “traveler” between the switches, but I’m NOT sure where it would connect on each switch, so even though I tested to see what connects to what, I’m still not sure how this SHOULD be wired so the switches work…

FWIW, we’ve wired in 3-way fixtures many times in the house but it’s always been when WE pulled the wire so we KNEW exactly what went to what. In this case, it’s all in there, the wire colors don’t help, and I’d rather not start switching wires randomly to see what happens!

I can TRY to make a diagram although I’m not sure with my lack of drawing skill a drawing help a lot. But, if needed I can try.

ALSO, if it's useful I can ALSO connect my wire to ground and see what wires in the switches connect to ground? Or IF they connect to ground?

I’m also not sure what other information to provide, so if you need more, let me know and I’ll try to measure what I can…

SO, from the above, or with whatever additional you need, can SOMEBODY out there tell me HOW these switches should be wired so the light works from either switch, just like any 3-way, WITHOUT getting extremely bright and blowing out bulbs?

I didn’t measure the voltage in the fixture, but if needed I can hook the bottom switch back up, and flip them into different positions and see what the voltage is, but it’s blown out incandescent bulbs, CFL bulbs, and currently there’s an LED in there, and I suspect if I give it a chance it’d blow that out too…

So, ideas? And “you’re screwed” is a valid one. It’s NOT worth rewiring the whole area just for this switch, so if the answer is “you’re screwed”, the bottom switch gets a cover plate and we only use the switch at the top of the stairs. But I can’t imagine it’s been this way since originally wired, so I’m HOPING somebody, sometime wired one of the switches wrong and it can be easily fixed.

Thanks for any help you can provide...
 
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Old 12-22-18, 11:35 AM
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WAY too much information and very hard to follow.

top right is green. I don’t THINK the colors mean anything.
Typically but green is never used as a current carrying wire..... even in a three way circuit.

With three way switches...... orientation means nothing. There is no up or down or left and right side screws. The ONLY thing that is important is the wire on the common or dark colored screw. The travelers are interchangeable.
With a three way switch circuit...... the common terminal at one of the switches is always live. The common terminal at the other switch is always switched hot and goes to the load/light.
 
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Old 12-22-18, 02:06 PM
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I just realized I don't know WHERE the green wire on the upstairs switch goes. I'll have to find out tomorrow when we get back...

I looked at a bunch of 3-way circuits, and I haven't found anything that looks like this one with hot feeds going to both switches...

pjmax, I know the traveler goes on the bright screws, and on this set it does. But having a hot wire going into the dark screw on the downstairs switch and another hot wire going into the bright screw opposite the traveler on the upstairs switch has me confused...

I'll figure out where the green is going tomorrow... Hopefully then I"ll be able to determine how the paths go and which wire must be in the wrong place. At the moment it SEEMS like the downstairs switch was installed "upside down" in that the power to the light is coming off one of the bright screws and the hot wire is going into the dark screw.

I'll play tomorrow, but is there something special I need to know when I have power to both switches all the time? Cause every 3-way I've found just has it coming into ONE of the switches.
 
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Old 12-22-18, 02:20 PM
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You cannot have power on the common of both three way switches. If you did.... the lights wouldn't shut off.

There are many ways to wire three way circuits but they all come down to applying the hot to the common of one of the switches. At that same switch...... one of the two travelers going out will be always live depending on switch position. The hot traveler and the dead traveler arrive at the second switch. Depending on which way the switch is.... either hot is selected and the lights are on or the dead wire is selected and the lights are off.

You must use a two wire voltage probe or tester or a meter for testing.
A non contact voltage probe is of no use here.
 
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Old 12-23-18, 06:09 AM
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Did you modify the wiring to these lights in any way?

Did you move breakers around in the panel?

You may have an archaic (now not compliant but possibly still grandfathered) 3 way circuit which, gets 240 volts instead of 120 because a breaker got moved in the panel.

In the diagram, if the left switch is up and the right switch is down then both terminals of the light are connected to hot (120 volts) for an expected difference of zero and the light is off.

But if the left source and the right source are on different legs of the 120/240 volt service then the hot to hot difference is 240 volts, not zero, and the light gets super bright and burns out shortly thereafter.

Green officially stands for ground (equipment grounding conductor). Using ground as a neutral often works but is improper.
 
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Last edited by AllanJ; 12-23-18 at 06:32 AM.
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Old 12-23-18, 11:58 AM
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pjmax, in this case I'm using a DVM. If I understand non contact voltage probe, I have one, but I'm not using it for this.

Unfortunately, if y'all speak electrician you may have to explain 'cause I won't necessarily understand the jargon.

allanj - We haven't modified the wiring in any way to this light. We haven't moved any wires or breakers in the box. This DOESN'T mean someone else over the last umpteen years didn't, only that WE didn't. A lot of the wiring was updated before we bought the house, but not all of it.

With all the wires off both switches, I confirmed that the green wire from the upstairs switch goes to the "white" wire of the light. Here's a drawing of the way it looks to me:


Then things went from "normal" bizarre to VERY bizarre...

I tried to find out WHERE the wire is that's the "common or ground" or whatever the white wire in a normal circuit is called... Feel free to tell me I'm doing it wrong, but here's what I did... Went downstairs to where the wiring has been updated and the plugs and such all have three wires (black, white, ground). At one plug I put the DVM on the top left and top right sockets. Got 120V. Put the top left into the ground socket. Got 120V. Put it in the top right and ground socket. Got ZERO V. To ME, that says I HAVE a proper ground for that plug. Right? Connected my wire to the GROUND plug.

With the circuit breaker OFF that turns OFF the LIGHT, and ALL the wires disconnected from BOTH (upstairs and downstairs) switches, I went to the BOTTOM switch and tested each wire for continuity to ground. And accidentally (don't ask) discovered there was 120V on the top left wire and the bottom right wire WITH the breaker off.

Went UPSTAIRS to that switch. The white wire and the black wire BOTH have 120V on them. Again, this is with the breaker that SHUT OFF the light OFF...

SO, shut off other breakers and found one that cut off the power to all the wires. With BOTH breakers off, there's NO power anywhere in either switch. B1 is the ORIGINAL breaker that shuts off the light. B2 is the OTHER breaker:

B1 off, B2 off - everything is off
B1 off, B2 on - top left and bottom right of the bottom switch, and the white and black wires in the top switch all have 120V.
B1 on, B2 off - top right of the bottom and black on the top switch have 120V
B1 on, B2 on - ONLY the bottom right of the lower switch and white of the top switch have 120V... This is where I originally was 'cause I didn't realize there were other wires that were hot...

Allanj, I looked at your drawing - what is the thing with the wire nut? Is there a traveler? Presuming the drawing above is correct, which from everything I measured this morning it is, HOW do I relate your drawing to what I have, and wire the bottom switch and/or the top switch so this thing works normally?
 
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Old 12-23-18, 12:06 PM
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I don't know how we can help you. You've got a green wire doubling as a neutral. You have two circuit breakers supplying this circuit. You basically have a mess on your hand. Usually I can visualize a circuit and pictures are extremely helpful. Random measurements on wiring are hard to apply towards the problem. Wire locations on switches is not helpful at all.

Ok.... I see you just added a diagram after I replied. You need to mark the C terminal on the switch.
That's the only important location.
 
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Old 12-23-18, 12:35 PM
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Do you have conduit, cable, or knob and tube? Are the wires covered with cloth or plastic?
 
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Old 12-23-18, 05:37 PM
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(The wire nut in my diagram was an exstraneous object, or you could say a wire not connected to anything in the 3 way circuit.

The diagram I show does not have any travelers although it can still work as a 3 way circuit. If this is what you have then you would need to string new cables to come up with an up to date code compliant circuit, with travelers.

What I called a 2 wire cable could well be two single conductors strung individually in the wall, called knob and tube wiring. K&T wiring is not code compliant nowadays.
 
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Old 12-25-18, 09:26 AM
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Something else to try:

Unscrew the light bulb. Tape the ends of your meter probes so only 1/16 to 3/32 inch of metal tip is exposed.

Part I

At the downstairs switch measure: voltage between your long ground wire and each switch wire (3 readings). What do you get? Flip the switch and repeat the readings.

At the upstairs switch measure voltage between your long ground wire and each switch wire. What do you get? Flip the switch and repeat the readings.

Part II

Put both switches in the up positions.

At the light fixture make 3 voltage readings. Lamp (bulb) socket shell to long ground wire. Lamp socket shell to socket bottom tab. Lamp socket bottom tab to long ground wire.

Repeat these last 3 readings for different combinations of switch positions.

Do not screw a light bulb back into the socket for now.
 
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Old 12-26-18, 09:50 AM
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I agree with the "you have a mess"...

The wiring to the DOWNSTAIRS switch is the cloth braided black wiring. It LOOKS like they replaced the knob and tube wiring everywhere in the house - the knobs are still there and in a lot of places the wires are still there, but so far they've all been dead.

The UPSTAIRS switch has plastic covered wiring, but it's white, black and green, and they're all attached to posts of the switch.

So, it's bizarre...

After all the bother with this, and drawing things, and fiddling with things, I decided the downstairs 3-way was "upside down" in that the wire to the light was not on the common.

So, I hooked it up the way it ORIGINALLY was, and indeed it acted as goofy as it did previously. So, I flipped the switch and wired it with the wire to the light on the common, the traveler on one side of the bright screws and the other wire on the other side.

AT THE MOMENT, it appears to be fine. When I measure voltage at the light, it's 120 or off. We tried all four combinations of switch positions, and it's always 120 or off.

SO, for the moment at least, it's now working as it should.

I'm not sure how they wired this thing, and I have no intention of trying to figure out what's in the inaccessible area of the attic or buried in the walls (I BELIEVE this area was the original part of the house from 1910, and it's been changed a few times in the intervening 100 years.

Thanks for the help everybody.
 
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Old 12-26-18, 12:39 PM
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Sounds like you have a California or Carter three way. Not legal any more.

Here is a drawing.

for some reason I can't load jpeg attachments that are only 16.2 kb
 
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