I’m having a problem with a 3-way lighting circuit that has me stumped. The situation is a flourescent kitchen light being controlled by two 3-way switches with power coming into the one switch box and a three wire exiting that box running thru the light and to the other switch box.
The problem is this. Sometimes when you first try to turn the light on at the one switch (the one on the end of the run) it won’t come on. If you then go to the other switch you can turn the light on … and once on, the light can then be turned on or off from either switch or any combination of switches. What is going on here?
I’ve already replaced both switches so I’m pretty sure the switches are not the problem (unless I purchased some defective ones). The wiring is all new within the last 5 years and has been working fine until recently.
Any thoughts?
Thanks! Dan
Replies
Most likely the fluorescent light is improperly grounded. Though it could be that the 3-way switches are improperly wired.
Or failing bulb or bad contacts. Many of time I have "fixed" tempermental units just by reseting the bulb.
I think you may have accidently hooked up one of the traveler wires to one of the common terminal on one of the switches.
Since the bulbs are working, I don't think that's the problem. You've also eliminated the possibility of a faulty switch.
Seems like the obvious answer is that you have the wires hooked up to the wrong terminal. Are you using a diagram to help you? Also, are you sure you've properly identified the "common" terminal on the 3-way switch? (Sometimes I use a multimeter to figure this out for sure.)
Thanks to all who have responded so far. I'm pretty sure the switches are wired correctly. When I originally did it a followed a diagram in the "Basic House Wiring" book by Monte Burch. I have since and before wired other 3-way switches the same way. But I guess it is possible I screwed something up with this one.
To answer your question about the common terminals ... they are black as opposed to brass looking so i don't think that would be the problem.
What has me stumped is this light worked fine up until recently. I was wondering if the colder weather may have something to do with it. Would the suggestion that maybe the hot and neutral are reversed at the light be more likely to be noticed if it was cold out?
Like I said, once the light is turned on at the one switch (the one with the power supply in) it can be turned on or off from either switch or any combination of both switches just like any other 3-way can.
Dan
you can quickly replace the lamp with a porclian lamp hold and bulb and verify that circuit works.
Yes, the cold weather is probably a part of your problem. If this unit is on the ceiling under an attic, it can get fairly cold up there. If you knocked a hole in the ceiling to feed the wire through and didn't seal it, it can get VERY cold up there, from air blowing through from the attic.(Remove the plastic cover on the fixture and see how cold it feels in there.)It may be worthwhile to go into the attic (if indeed the fixture is below an attic) and pile on some more insulation in that area (and also seal any ceiling penetrations).Are you sure the fixture is properly grounded? Ie, you connected the ground wire from the romex to the fixture, and the other end of the ground wire is appropriately connected. Fluorescent fixtures depend on a good ground to "ignite".Are you sure you have the correct polarity everywhere -- black to black and white to white? Incorrect polarity will cause problems.You can try a trick of wrapping a piece of wire around one end of one lamp, about an inch from the end, and grounding the other end of the wire. If it doesn't work at one end of the lamp, try it at the other end.
Check out thread 51667.1 .
The possible miswiring would be wiring it a la K&T vs the "modern" approach of using travelers. Thin incorrect approach would fail to maintain the proper hot/neutral orientation at the lamp, causing it to switch depending on the relative orientation of the two switches.
Once the fluorescent has been lit and run for several seconds, it's warm enough that it will probably come on regardless of any problem present.
Dan,
>>by two 3-way switches with power coming into the one switch box and a three wire exiting that box running thru the light and to the other switch box.
That means that you should also have a 2 wire coming back to the lamp from the secondary switch.
Is this the case?
What is the ground wire situation?
SamT
Yeah, that discription bothers me a little. Sounds a tad like a K&T style circuit, which would definitely cause this problem.
When I say 3 wire I am talking about a romex cable with one black, one red, one white and a copper ground. So maybe that has caused some confusion. According to the book I've been using to wire all my 3-way switches for about six houses (apartments I own) you can wire a 3-way switch running 3-wire from the switch with the incoming power then to the light with a further 3-wire leg running from the light to the other three way switch. It might not be the most common way of doing it but it does work. An all the wiring I do is old work wiring so sometimes it is the easiest pathway to take.
I will go back and make sure all my connections at the light are correct and secure and I'll trouble shoot it by temporarilly taking out the flourescent light and replacing it with a temporary socket.
When you say a flourescent light needs a good ground to work (or somebody said it in their response) does that mean a flourescent light would not work in a house that only had k&t wire or the old 2 wire romex before they added a ground?? Just wondering.
Dan
Dan,
The red and black wires from the power-in switch must connect only to the traveler terminals on the secondary switch. They must not connect to the lamp.
The white from the power cable white must connect to the white in the traveler-to-the-lamp, thence to the lamp neutral.
The white from the secondary switch common terminal must connect to the lamp hot.
You know, of course that the black in the power feed romex must connect to the primary switch common.
The ground, obviously, is connected everywhere.
Also check for marginal connections.
If you have a VOM or ckt tester, check that the power feeder black is hot to ground and the white is zero volts to ground.
SamT
Let's see if I can do this --
K&T style:
hot --o o-- hot
====o------(lamp)------o====
neut -o o-- neut
Correct style:
o--------------o
hot --o==== ====o------(lamp)---- neut
o--------------o
Great response Dan! Even us old foggers get to learn here.
I'd heard of your K&T method, never really thought anybody did it that way. (pre litigation for a kid sticking his finger in the socket) , and always thought that method was just 'made up' as a horror story aka who could be that dumb? - have you really seen this wired like that?
Pop rewired our house when I was a kid and did the leftover K&T like your 'correct' schematic. There were no 3-way circuits in the original wiring.
they certianly do...
PITA to trouble shoot...
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming
WOW!!! What a Ride!
I've seen the K&T style in a house built ca 1910, wired with a 120V K&T service at that time, and subsequently updated with a 240V service. The 3-way switches in question controlled a light in the stairway to the attic. The arrangement made itself apparent because one of the "off" combinations of the two switches was "off permanently" -- it caused the bulb to burn out.