In article , Scott wrote:
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?

Maybe the switch needs replacement. Maybe most likely the switch needs
replacement.
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
"neutral".

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 fixtu 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.

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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
http://www.misty.com/~don/dschtech.html)

- Don Klipstein , http://www.misty.com/~don/index.html)