How we got here:
After putting up a new ceiling light, another set of lights in a different room, but on the same circuit wouldn’t turn on.
The second set of lights was in a three-way configuration, with one switch being an electronic security timer; while the timer function was rarely used, the lights/switch had been working just fine for over 10-15 years.
First check revelled that the timer was not working (not even the clock fuction) and several attempts to reset it failed. It was decided to replace the timer with a standard 3-way switch.
Switch is installed, power restored, light turns on/off; but, lights won’t turn on off at old switch. Wires are switched, now another combination of on/off between the 2 switches won’t work; switched again, yet another combination won’t work.
Time to get serious, got out a set of jumper leads (alligators at both ends), make up a matrix, and test each connection combination (i.e. each of the 3 wires has been connected to the common while the remaining 2 in each case were tried both ways on the other connections; every combination will turn on the lights in at least one combination; but, none in no case will the lights turn on/off in all combinations.
What next ?
is there a static test for 3-way switches (continuity/buzz ?)
do these switches sometimes fail ?
is the path of leat resistance to assume one or the other switches is no-op and just replace both and see what happens ?
is there a way to test which wire does what (curently have 1 3 conductor (red/black/white) and 2 conductor (black/white) where the white from the 2 conductor is connected to the black in the 3 and the remaining red/white/black connect to the switch . they were connected to w/r/b leads on the electronic timer, but I have no documentation to verify which lead did what.
Phill Giles
The Unionville Woodwright
Unionville, Ontario
Replies
The 3-way will have a common terminal and 2 traveler terminals.
You can ID them by the color of the terminals. The common will be a different color than the travelers. I think that the common is dark or gold and the travelrs silver, but it might be the oposite.
You should have continuity between the common and one traveler with the switch in one position and with the other travaler with the switch in the other position.
Most common failures is in the movement and you will feel it, but there is possibly a bad connection from one of the terminals to the contact.
"is there a way to test which wire does what (curently have 1 3 conductor (red/black/white) and 2 conductor (black/white) where the white from the 2 conductor is connected to the black in the 3 and the remaining red/white/black connect to the switch . they were connected to w/r/b leads on the electronic timer, but I have no documentation to verify which lead did what."
It does not mater as long as then are the same at each end in relation ship to the 3-ways.
But there are connections other connections. Where is the power feed and where is the light connected to that circuit.
Also what wires where in the boxes for the other lights you changed?
The light that was changed was a simple b/w connected to a regular switch; power came from the switch's box, it was not touched.
Is there a test protocol to see if the internal switch inside the switch is working ?.
Phill Giles
The Unionville Woodwright
Unionville, Ontario
As I say the you should have continuity between the common terminal and one and only one of the traveler terminals with the switch in one position.
With it in the other position you should have continuity between the common terminal and the other traveler terminal.
Curiouser and curiouser. The second 3-way switch (i.e. the one that's hasn't been touched as yet) has a jumper from the "common" to the terminal wired to Black. What's with that ? The only thing I can think of is that it's part of the wiring for the electronic timer/switch that was formerly in 'box #1'.
'Box #2' is a little scarey for other reasons, there are 2 two-way switches in there, both on entirely different circuits - you have to pull 2 breakers to takes its bite away..
Phill Giles
The Unionville Woodwright
Unionville, Ontario
"The second 3-way switch (i.e. the one that's hasn't been touched as yet) has a jumper from the "common" to the terminal wired to Black. What's with that ?"
Hard telling.
You really need to draw the whole thing showing the cables and connects at both ends.
Solved.
I should have figured this out earlier. The electronic security switch (you know the kind, they replace a switch and turn lights on and off at set, or optionally on this model, slightly variable times while still functioning as a switch - they have a visible clock) needs modified wiring.
The switch needs to have power going through it all the time to run the electonics (I have other versions where the clock is battery-powered) and passes a continuous trickle current through the lamps. So, in order to do this in a 3-way configuration they jumper the other switch so that it's always "on" and turn the lights on and off with an electronic reversing relay: the momentary break in the flow as the second switch passes through neutral is waht turns the light on and off (a push-button on the timer does the same). It literally converts it into a NOn,SPST-MC switch.
.
Phill Giles
The Unionville Woodwright
Unionville, Ontario
Phill,
Here's a good thread on 3-ways.
http://forums.taunton.com/n/mb/message.asp?webtag=tp-breaktime&msg=43905.23
SamT
that would be http://forums.taunton.com/n/mb/message.asp?webtag=tp-breaktime&msg=43905.1 I believe, the theory was not the problem, what I needed was a test to find out why a working 3-way connection suddenly stops working..
Phill Giles
The Unionville Woodwright
Unionville, Ontario
Does this look like what you've found so far?
View Image
SamT
Not really, and my drawing software is on another machine. The only real trick is that black is the common in box 1 and white in box 2 while red is a traveler
BUT, took the jumper off and the circuit works just fine (and me with a bag of new Levitron Decora 3-ways c/w nylon cover plates ready to replace the whole shebang - guess I will anyway.
Phill Giles
The Unionville Woodwright
Unionville, Ontario