On 04/06/09 11:03 pm I wrote:

I replaced some existing incandescent bulbs by LED bulbs, then
noticed that they do not switch off completely but still glow dimly.

LED? You don't mean compact fluorescent? I havent' seen LEDs that
fit wthout changes.

But in the kitchen with a timer in place of the wall switch, I
couldn't get my CFL to turn off. Do you have a timer in the circuit.

Checking the voltage at the lamp socket with a high-resistance
electronic multimeter, I get a reading of 48v!! A few volts might be
OK -- induction, stray voltages, etc., but 48V!!!

This occurs in two different rooms, but I think the various lighting
circuits are all connected to one breaker.

I hadn't measured the voltage in the second room, but I assumed that the
glowing LEDs after switching off had the same cause. In fact this was
simply a brief "decay time," probably as a capacitor discharged.

A timer in each room, and on lamps, seems unlikely.
What could cause this?

I'm going to guess here that you have some kind of electronic switch,
i.e. a dimmer or something similar. As long as there is enough voltage
to turn on the LEDs, a small leakage current from an electronic switch
could make them glow dimly.

No. Regular "mechanical" wall switch.

Possibly a lighted mechanical wall switch?

No light in the switch.

It turns out that it was a lighted switch after all -- but no light had
been visible in the switch with the CFL bulbs that I replaced by LED.
And even when I had the switch hanging out of the wall. the "Lighted"
label was on the side away from me.

Perce