** 3-way electrical light switch (strange problem) **

Hey All,
I have a room I can enter from two different doors. Each has a rocker type switch on the wall. The lights are flouresant tubes. Suddenly one of the switches needed to always be in the down position in order for the lights to have a chance of going on while using the other switch. If this particular switch was not in the down position, then the lights would always be off no matter what I do to the other switch. I went to Home Depot and changed out both switches. It fixed the problem completely for about 2-3 days.. Suddenly the same problem is occurring again (now with the new rocker 3-way switches). How could this be? Anyone have any idea what is going on here and how to fix this problem?
Thanks a bunch for the help!
-David
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David wrote:

    Bad connection between the switches or at one of the switches? Check the switches out with an ohm meter with power off of course.
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You probably have a loose wire somewhere. Either at one of the switches or if the fixture is in between the switches electrically, somewhere in the connections there.
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So you mean that possibly a wire is not tightly screwed down on the switch properly? Or at the "fixture" between the switches? What "fixture" would that be? Is there a fixture device which allows for 3-way switching? Do I need to find something ? Or are you speaking of the lighting balast?
-David
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By fixture, I meant the light fixture. If the wires go from one switch to the light and then to the other switch the problem could be located in the light fixture in a connection.
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I would think if there were a loose wire at the fixture, the light would be intermittent or not work regardless of switch position.
The wires that go only between the two 3-way swtiches are called "travelers". One of them could be lose at either end, and there could be splice somewhere in the middle, in a box.
Again I ask, how did you know which switch was bad? Because that is the one at the top of the stairs that you usually use? Hmmm. Irrc, you replaced both. So maybe it wasn't a switch..

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The wire does not always go from one switch directly to the other. The light can be in between and when this is the case the traveller wires are connected together at the light. There could be a loose connection there.
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On Wed, 14 Feb 2007 15:52:45 -0500, "Frank Ketchum"

True.
Oh, I see what you meant. I took "at the fixture" too extremely.
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What about the other switch B? Didn't it have to be in a particular position also? Because if switch A stays in one position, only one of the two positions for B will be "on". How did you know which switch was the problem?

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For a properly installed three way system to work, you need a three wire cable to go from one switch to the other. sometimes this cable doesn't go directly from switch box to switch box, but instead, goes from each switchbox to the junction box that the light fixture is attached to, and splices are made there. If your system did indeed work properly after you installed new switches, but not now, you have a loose connection somewhere. It could be at either of the switches, or in a wire nutted connection in either of the switch boxes or in the lighting outlet box as Frank ketchum describes

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Assuming the most common arrangement,
The way the switchs work is something like this: ---------<==============>----------* Where the < and > are switches, and the === is a pair of travellers between the switches.
Normally, power comes in from the left, and switch < sends it to either the top or bottom traveller, and switch > either collects it from the same traveller and sends it on to the light *.
From your description, one of the travellers has either come loose at one end or the other, or has an intermittent break in it, or one of the switches is failing to make contact in either the up or the down position.
If the light comes on with both find a combination of position that makes the light come on. Then flip both switches once. The light should come on in that position also. Since it doesn't, try rattling the switch levers side to side. If the light comes on, or the switch spits a spark, then that's a bad switch.
If you get no results, take both switches apart, after noting what wires go where, and check each traveler for continuity. If you don't have continuity, pray that there's a junction box or something between the switches where it's come apart. If you do have continuity, replace both switches.
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Sometimes an installer will cut a wire too short and will pigtail it to make an extension of a wire. Look in the box for an extra wire nut which joins two pieces together to make a longer one. It's a stretch that this is the problem but hey, can't hurt to look.
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