Weird Three-Way Switches. Help!

10 years ago

We have two three-way switches (we think) at either end of our hallway. One of the switches is a dimmer switch. The other is not.
The switch at the entrance to the hallway, the dimmable one, will turn on the light. Then, we go to the end of the hall, and turn off the light with the other switch. If we go back to the entrance and flip the dimmable switch, it won't turn on the light again. Moreover, if after doing that step, we go back to the end of the hall and flip the other switch, it won't turn on the light again.
The only way we can control the light is to either turn it on or off from the entrance dimmable switch, or if we turn it off at the other end, then we have to turn it back on from that end.

Some additional details from opening up the switches:

The entry dimmer three-way switch: The black wire is hot. The red wire appears to have been inserted in the "common" hole.

The other non-dimmer is also a three way switch. But on this end, the white wire is hot. And the black wire was in the "common" hole.

So, I thought this was simple, and put flipped the red/black wires, so that the red wire would be in the "common" hole, like in the dimmer three-way switch. When I did that, however, nothing worked at all. So, I returned everything the way it was, and the lights work as before, but not properly as a three-way should.
What's going on? How can we fix it?

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Comments (5)

Ron Natalie
10 years ago
Are you sure this is a three way dimmer?

Usually with three way switches the common goes to the light on one end and the power feed on the other. The two travellers go to the two throws of the switch.
elltwo
10 years ago
There may be a fourway in between, (electrically). De-construct it at the switch boxes and the fixture and make sure you can account for each conductor and its source and destination.
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Coeng Assuming that the switches worked previously, and that only the switch terminal connections are wired wrong, I advise the following procedure. If you are comfortable using a voltmeter or a neon tester. Follow these easy steps (for 2 -3 way switches). 1) Turn the power OFF and physically remove both switches, and take off the wires from the switches only, leaving 6 exposed wires (3 in each box). Leave the GROUND WIRES on the switches. Seperate each wire so they do NOT touch each other or the switch box. 2) Turn the power ON and identify the HOT wire (it will be the only one of six that has voltage). Measure between each wire and the metal boxes or GROUND WIRE until you find it. [Mark this wire]. Then turn power back OFF. 3) The HOT wire found in step 2 is the COMMON, and goes on the DARKEST screw of the switch. The other 2 wires can go on either of the two remaining screws. Wire this switch back up (call it switch#1) and put it back into the box. This switch (#1) is now correct and you can focus on the other box (Switch #2). 4) Turn the power back ON and identify a HOT wire at switch box(#2).Then toggle the (#1) switch and identify another HOT wire at box (#2).The COMMON wire at this (#2) switch box is the wire that was NOT HOT . [Mark this wire]. 5) Turn power OFF, and wire up the second switch. COMMON, wire goes on the DARKEST screw of the switch and wire up the two HOT wires to the two other screws. 6) Switches are wired right when BOTH switches are "down" and the light is OFF. If not just reverse both "Traveler" wires on one 3 way switch. Have A Nice Day Linesman
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In addition to that when following the steps in the other post about trouble shooting a three way switch, i found out that with one switch out of the box completely ( no wires connected) and the power on the other three way switch could still control the light on and off. The wiring worked before and it was a three way not a four way switch that was installed, and I changed nothing but the two switches. I also ran a continuity test and swap both three way switches to see if that was the problem - it was not. I'm at a loss here as to how to proceed next. Thanks again.
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Yes, this does sound like the circuit and/or switches are miswired. One quick check you can make is to look at the switch toggles. Do either or both of them say "on" and "off" on the moveable switch levers? If so, that's most likely your problem: you have a two-way instead of a three-way switch. (Three-ways don't have "on" and "off" in raised letters, but are smooth instead.) Expanding a bit on what joed's requesting, could you take off the switchplates (covers) and look at the wiring to the switches? Just to be safe, turn off the circuit breaker for that lighting circuit first. Here's what you'll be looking for: Because I'm guessing that this is relatively new wiring, each of the switches should have a total of four terminal screws. One, which usually has a green tint to it, should be connected to a bare (or green) ground wire. That leaves three posts for the current carrying wires. If there are only two wires connected (not counting the ground), that's a problem because properly wired three-ways will have three current carrying conductors attached. Of those three current carrying terminal posts, one is called the "common" and it is usually tinted differently (e.g., black) than the other two (e.g., brass or silver). Also, the common is usually at the other end of the switch from the other two (the "travellers"). Once you determine which is the common, can you make us a "map" something like the following: Switch #1: Black wire on common, black and red wires on the two travellers. Switch #2: White wire on common, black and red wires on the travellers. I'm not suggesting this is the only correct pattern--it's not--but it's an example of the information that will help figure this out. Also helpful would be documentation of what happens with the switches in various combinations. Here's an example of what I mean: Switch #1 up, switch #2 up: lights on Switch #1 up, switch #2 down: lights off Switch #1 down, switch #2 up: lights off Switch #1 down, switch #2 down, lights on Again, I'm not suggesting right or wrong answers, just the format.
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The only way I can think of off hand to get a pseudo series circuit is if the wires are all pinched together behind the light fixture transfering some of the power. I doubt the wires are long enough to transfer that much voltage under normal circumstances. Unless the metal of the conduit is acting like a transformer, but the ground continuity would probably need to be broken or have a high impedance path back to the panel somewhere. This sounds more likely only because it is effecting all three wires at the same time, even when totally disconnected
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thebigad
Original Author
10 years ago
Not sure of the fourway - wouldn't that mean there is another switch involved? Sorry, I'm not good at wiring.

When you say de-construct it at the switch boxes - do you mean unscrewing the light switches and evaluating the wires behind? I tried that before, but may need to do so again.

ronnatalie brought up a good point - I need to make sure there are two travelers. I thought it was a three way simply because both light switches control the same hallway light.

The other option I was thinking of, and maybe you all can help, is there a way to just replace the current two switches with a motion sensor version? That way, I can always leave it on and if somebody walks by, the lights will come on.

Thoughts?
elltwo
10 years ago
The 4way suggestion involves another switch. The way you described wires in holes may mean the switches were "backstabbed" and these connections can fail more often than wires that are curled around the screws and held in place by tightening the screw.

This failure could have happened in the unknown 4way(s). If you can establish that all of the wires begin and/or end in the two switch boxes or at the fixture then there is no other switch, but, if there seems to be wires that appear from nowhere or disappear to parts unknown, then you may have a buried splice or one or more 4way switches.

The black wire that is hot at the dimmer is also hot at its other end unless it's broken, the same holds true for the white at the other switch. One of the common terminals should always be hot, that's the one that comes from the panel either directly or from another accessible splice. The other common should only be hot when power is sent to the light. The two screws that are the same color on the non-dimming switch should alternate between hot/not as either switch is thrown.
bus_driver
10 years ago
First one assumes that this setup worked properly at some previous time. But that is not specifically stated. Did this problem start after someone changed something about the installation-- like installing a dimmer? If so, restore it to the previous setup. One failed traveler (connection) might cause some of the symptoms described.

This post was edited by bus_driver on Thu, May 23, 13 at 9:00

Weird Three-Way Switches. Help!

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Ron Natalie

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Weird Three-Way Switches. Help!

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Ron Natalie

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