My daughter just bought an older home & she tells me that one of the ceiling bedroom light doesn't turn off completely when she throws the switch. The bulb still glows dimly as it appears to be still getting getting a trickle of electricity even with the switch off. (she unscrews the bulb to shut it completely off) With my limited knowledge of electrical circuits, I told her I would come over & replace the wall switch. (assuming it is the culprit) Any thoughts on what else it could be?
I can think of several possibilities. The most likely one is that she has a dimmer switch on that circuit and it is not turning fully off.
Another possibility is that she has a wiring problem where the wires to a powered circuit are close to the wires between the switch and the light in such a configuration that they are forming a transformer. I just find this one very unlikely.
I suppose it would be possible that there is some sort of other wiring problem like a three way switch with a bad connection somewhere?
It is also possible that someone has set up the circuit to act like a night light. A diode or a resistor wired in at the switch could do this. I would think it would be more likely in a bathroom, than a bed room, but maybe it was once a child's bedroom and they wanted a full time night light.
Assuming it's an indancescent bulb: That's a good place to start. However, be VERY careful because this -could- be caused by crossed wires someplace and turning off the breaker may not actually remove all power from the lines. Be certain there is no power on anyh of the wires in the box when you turn off the ckt breaker. A dim light bulb is getting plenty of current to still be very dangerous, as in lethal, to you.
Also, pease post to ng's in Text only. Your post is in html.
Assuming the "switch" is a conventional toggle, I've never encountered one which developed enough "off" leakage resisistance across it to make a ceiling sized light bulb glow. If by some strange chance it *is* just the switch, then it should feel a little warm if left in the off position with the bulb glowing, in which case it's worth taking a shot and replacing that switch.
Bt, if it doesen't feel warm then I'm going to take a tack I seldom do on this newsgroup and say, "Leave the switch off and the bulb unscrewed and get a pro in there ASAP."
It could be something as benign as the deliberately installed diode or resistor Joseph aluded to (I'd hate to think there's a naked power resistor hidden somewhere in the wall.), but if not, there's something seriously ungood with the wiring for that ceiling bulb and it's unlikely a neophyte without test equipment will be able to find it without possibly causing more things to go wrong.
No offense intended, Dick, just playing it safe for your daughter and you.
The only thing I can think of is one of those illuminated switches if you're feeding a VERY low power bulb - they leak a little current on purpose to illuminate the switch. Impossible with an incandescent bulb, but it's possible that certain kinds of fluorescents _might_ glow dimly from the leakage current alone.
If it is a fluorescent, it's also (remotely) possible that a very high power electromagnetic field nearby is energizing it. If so, it'll light up even when unscrewed from the fixture. This behaviour is usually only seen inside a lab, but if you have a very high voltage distribution line nearby it's (just barely) possible.
This is a good recommendation actually, but first, look to see if there's a dimmer somewhere or diode disk installed (it'll be a small disk in the lamp socket. Kill power before attempting to remove it).
Any wiring fault that results in severe dimming of lightbulbs or other signs of drastic voltage reductions is essentially 100% guaranteed to be overheating something, probably pretty badly, and is potentially VERY hazardous.
You need to get the power to that circuit turned off until you can identify and fix what's wrong.
bedroom light doesn't turn off completely when she throws the switch. The bulb still glows dimly as it appears to be still getting getting a trickle of electricity even with the switch off. (she unscrews the bulb to shut it completely off) With my limited knowledge of electrical circuits, I told her I would come over & replace the wall switch. (assuming it is the culprit) Any thoughts on what else it could be?
Well, this is odd. Two things come to mind:
- look at the bulb base and see if it's a tri-light bulb and socket. Maybe they've jury-rigged a nightlight by wiring the low-wattage filament to always-on power and the high-wattage filament to the switch. Though I really don't think I'd want a ceiling light on all night.
- illuminated switches work by running a small current through a bulb in the switch handle in series with the load, when the switch is "off". Normally this is not enough to cause the load to illuminate but maybe there are odd failures that allow more current to flow ... like the bulb in the switch has decreased in resistance somehow.
If the home is old enought it may have knob and tube, and you may find hot and neutral wires taking completely different routes through the house. It's also not unheard of to find switches in the neutral leg, and (if a real hack worked on it) fixtures wired with neutral connected to a different circuit than their hot leg. Any of those can make diagnosis difficult, and the latter two increase the danger of working on stuff.
It is possible that one of the hot wires has the shielding damaged and could be touching the neutral or the electrical box itself. This would cause just enough electricity to pass to make the light glow. If your power panel is fuse based, this electricity is not enough to 'blow the fuse'. I would check the switch to make sure there is no current before you replace the switch.
Before you go over to her house, stop by HomeDepot or Lowes and buy a new standard switch, they are about a dollar and easy to replace. Then you won't have to do anything else if that turns out to be the problem. Let your daughter buy a new faceplate if you leave the new switch in. Most only have three wires--one is ground. Some only have two-no ground. Switches with more than three wires are two/three way switches.
I would bet that the wiring was screwed up. If the new switch doesn't change anything, which I doubt it will, try and trace the wiring. Also, see if there are any other switches that might affect the circuit.
My daughter tells me that the light that glows is in a bedroom ceiling & controlled by a normal (non-illuminated) wall switch......but that in the upstairs hall (outside the bedroom) there is a ceiling light that is a 3-way (switch at the bottom of the stairs & illuminated switch at the top of the stairs) but that the lower switch has no control unless the hall light is switched on upstairs first. Figuring all these may be on the same circuit, my plan is to replace both 3-way hall switches first & then, if the bedroom light still won't shut off, to replace that wall switch as well. Any thoughts?
As for the three way switch, it would appear one of the runners is broken or is not connected at one end or the other. It is also possible, but IMO less likely a bad switch. Of course it is also possible that someone has replaced one of the switches with a normal switch. Anything is possible.
Don't just replace the switches, get a tester and/or some batteries, and map put exactly what wires go where. This bedroom light is a round dimmer-switch that you twist to dim, and push to shut off, is it?
This is a fairly common problem with knob and tube wiring. Power is back feeding into the neutral wire. Could be happening anywhere in the circuit or another circuit for that matter. Sorry I can't be of more help without seeing it.
I would kill the circuit and replace the switch. In the process you may find something unusual like a capacitor or a resistor across the switch terminals. May be some anomaly in the switch. If the new switch fixes it you are home. If not, you're back to square one. Seems like a reasonable first approach to the problem. At least, it's quick and cheap.
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