In a rental house I take care of, theres a fluorescent light
fixture on the ceiling of the kitchen. The fluorescent lights
in the fixture are flickering on and off, even though the wall
switch is turned off. What's likely to be the problem there?
Most likely, the earth ground is missing or has opened up
Was it worked on lately? Maybe it's miswired inside the fixture.
Not much else can cause one to flicker with the switch off.
| In a rental house I take care of, theres a fluorescent light
| fixture on the ceiling of the kitchen. The fluorescent lights
| in the fixture are flickering on and off, even though the wall
| switch is turned off. What's likely to be the problem there?
Please stop top-posting.
A defective switch would be my first thought. A kitchen is a high
use area and a cheap switch may have worn out. I've used "industrial"
grade switches and sockets whereever I have to replace anything in my
own home. It's $0.39 for a homeowner grade unit, $3.90 for commercial
and probably $5.95 for industrial grade ( at home depot ).
I don't particularly enjoy simple electrical repairs; I want to do the
job one time and have it last until after I die of old age. Spend the
six bucks and forget about it.
My Dad had a fluo that flickered. I can't remember the wiring, but he ended
up wiring a double pole double throw switch to the unit. The fluo was in the
darkroom, under the edge of the film and paper trimmer. So the light was
double definitely not welcome at that location.
Maybe the switch needs replacement. Maybe most likely the switch needs
But any of a few other things may be happening:
1. The switch is on a piece of Romex branched out of the fixture or a
junction box, so that the Romex going to the switch has an "unswitched
hot" and a "switched hot" and no neutral.
The capacitance in such a cable passes a very small amount of current,
and some fluorescent fixtures could possibly very dimly glow or do a "dim
strobe" sort of thing as a result. If the grounding conductor is not
grounded, then ground it - that will shunt to ground most of this current.
If the cable lacks a grounding conductor, I don't know what to do then
except replace the cable with one having a grounding conductor or replace
the ballast with a different type of ballast, or put an incandescent lamp
(or some other load - it can be a light load) in parallel with the
fluorescent fixture. Or move the switch (or run new wiring) so that the
switch is connected to Romex that has its white wire working as a
2. The fixture needs to be grounded, although this is not the usual
reason. Slight chance current is conducting capacitively from a
nearby unswitched hot conductor, although I do not beleive this
usually makes fluorescent bulbs glow in the dark. (The usual reason for
grounding a fluorescent fixture: The electric field distribution within a
fluorescent bulb that is trying to start is more favorable if the bulb is
within half an inch of grounded sheet metal.)
3. The switch is not a simple switch but some electronic type, maybe with
extra features, and lets through a trickle of current when it is off.
One example is Radio Shack's "Plug 'N Power" system - the switching
modules pass a small trickle of current to determine presence of a load.
They do this so that they can turn on if a conventional switch is used in
addition, in order to make the additional conventional switch usable.
This should be fixed. Fluorescent bulbs may suffer excessive wear from
making light while having their filaments at a temperature other than
their normal working temperature - whether too hot or too cool.
(Rather technical details on this are in
- Don Klipstein ( firstname.lastname@example.org, http://www.misty.com/~don/index.html )
Two things come to mind.
1. Be sure there is not a bad connection in the neutral feeding that
fixture. Is there some other light or outlet that when used triggers
the problem? If YES, trace back from there.
2. Is there a high voltage device in use near the fixture, or on that
same circuit? For example, I am a farmer. If I take any florescent
bulb, and hold it near my electric livestock fence, it will light up.
Its not connected to anything. I am just holding the bulb in my hand,
and when I get it a few inches from the electric fence, it lights.
This is a great trick to test an electric fence without touching it,
or buying a fence tester.
Okay, I found the solution! Or, rather, my wife, did. We visited the rental
house today, and my wife discovered the obvious. There's a second wall switch
on the other side of the kitchen. That's the swtich that turns on the fluroescent
light in question. In short, I was switching the wrong wall switch on and off.
Gosh, I feel so dumb (as I should)...and now I feel very humble. Thanks for the
great suggestions, though, and for your efforts to help me out.
If anyone wants to post a compliment for my wife, please do. I'll be happy to
print it out and give it to her.
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