I have an outdoor light over my barn doors that has had a led bulb in it for roughly 5 years. I had to replace the original bulb about a year ago as it was the older design with open slots in the bulb covering which had become half filled with dead bugs.

The new bulb worked fine for about 6 months and then it started staying lit with a steady glow even when the light switch was turned off. It does this all the time that it’s off. You can clearly see it even in the daytime.

Nothing has changed as far as any wiring goes. I’ve tried several other brands of LEDs but they all do it. Most if not all of the bulbs that I tried were better quality and rated as being dimmable as most bulbs are these days.

One thing I noticed, when trying different bulbs, I shut off the breaker that feeds the barn and garage thinking that it might reset something. When I did that with the barn light turned off, the light stayed dark. As soon as I energized anything on that circuit (I hit the garage door opener), the barn light started to glow again.

 

Welcome to AAC!

Does the bulb behave if installed on a different circuit?

Have no idea why it would work for 6 months, then act up...

 

it started staying lit with a steady glow even when the light switch was turned off. It does this all the time that it’s off. You can clearly see it even in the daytime.

How about your light switch? Has it neon or LED indicator ON/OFF?

 

Ants tend to colonize surprising places. I once had a light switch stop working. When I opened it out fell dozens of ants. Your leakage might be coming from something similar. Otherwise, why does this worry you? (other than this leakage was not intended.)

 

I have the same issue with 2 outside lights. I had old style LED bulbs and they worked fine, as did the even older incandescents.
The cause in my case is stray capacitance. The wires are long and somewhere in that cable run AC voltage is causing enough current to flow downstream of the light switch. remember, LED bulbs draw a lot less current than older incandescents, so the stray voltage is enough to partly light the LED bulbs. Older LED bulbs amy be less efficient and so draw more current, sufficient to load the srya voltage to a point where there is no light emmitting.
The new LED bulbs i used are the ones with clear glass and LED "filaments" so when they glow it's really obvious. Close inspection showed that the old LED bulbs also glowed but I just didn't notice it.
I spoke to an electrician friend of mine and he agreed, stray capacitance. I can either put an incandescent bulb in the circuit to load it or add a capacitor to the light socket to load the circuit.

 

Welcome to AAC!

Does the bulb behave if installed on a different circuit?

Have no idea why it would work for 6 months, then act up...

MY personal experience with LED's that wouldn't shut off had nothing to do with the bulbs themselves. Rather, it was the type of switch I was using. It was a motion detector light switch. When you walked into the laundry room the light was supposed to come on. It did exactly that when running incandescent lamps. But when I switched to fluorescent or LED lamps the power would continue to flow and the lights would remain somewhat illuminated. I discovered that if I put just one incandescent lamp in circuit the automatic switch would finally shut down. I've since replaced that older motion detector light switch for a newer one. Now, even without an incandescent lamp in circuit, the lights fully shut off. That's MY personal experience.

Since none of us can be there to examine or test the circuit none of us can know the exact cause; why it would work normally for a while then begin to act up all of a sudden. So MY question to you is "What kind of light switch are you using?" It's possible that an older type of switch may be in the beginning stages of failure. Especially if it's purely an electronic switch. There are no circumstances I've ever encountered where a light switch (mechanical type) can pass current when the contacts are open. Unless, as @DickCappels suggests, insects might be the cause of some current passing through. If that's the case then perhaps a new switch may solve the problem.

 

Certainly the comments relating to leakage currents are correct. A high output LED tends to start emitting a small amount of light at a much lower current than the rated current specified for the rated illumination output. So it does not require much leakage current to produce a bit of illumination.
You can verify that if you are able to measure the voltage across the LED bulb SAFELY, with a digital meter. The leakage current may be simply due to capacitive coupling between the wires in a long cable to the switch.

 

Certainly the comments relating to leakage currents are correct. A high output LED tends to start emitting a small amount of light at a much lower current than the rated current specified for the rated illumination output. So it does not require much leakage current to produce a bit of illumination.
You can verify that if you are able to measure the voltage across the LED bulb SAFELY, with a digital meter. The leakage current may be simply due to capacitive coupling between the wires in a long cable to the switch.

See my answer above..

 

Thanks for all the thoughtful responses and suggestions. To answer some of the questions, the led bulb behaves normally in a lamp inside the house. It is a long run from the house to the barn. The switch inside the house that controls it is a normal toggle switch with nothing out of the ordinary. I did try replacing the led with a cfl today. When I first put the cfl in, it flickered like a strobe light but at a low level of light. When I switched it on it behaved normally. Turned it off and within 5 minutes the flickering had subsided substantially. Thirty minutes later it isn’t even visible. Once it gets dark I’ll know for sure if it has gone away.

 

It is a long run from the house to the barn.

I used to have a switch running from my garage to my barn about 100 feet away. Unfortunately, I never replaced the lights with LEDs and that switch is no longer used because the barn has its own power meter now.

When I first put the cfl in, it flickered like a strobe light but at a low level of light. When I switched it on it behaved normally. Turned it off and within 5 minutes the flickering had subsided substantially. Thirty minutes later it isn’t even visible. Once it gets dark I’ll know for sure if it has gone away.

Fluorescents have a long after glow period. I remember doing an optics experiment in a school closet/storeroom and had to sit for quite a while waiting for the fluorescent tubes to stop glowing.

 

I used to have a switch running from my garage to my barn about 100 feet away. Unfortunately, I never replaced the lights with LEDs and that switch is no longer used because the barn has its own power meter now.
Fluorescents have a long after glow period. I remember doing an optics experiment in a school closet/storeroom and had to sit for quite a while waiting for the fluorescent tubes to stop glowing.

This was when I first put the cfl in and before it had been energized.

 

Very typical normal misbehavior of some LED bulbs staying faintly on from capacitive leak of wiring while switched off. Nothing is wrong anywhere., bulb or wiring. Enjoy the aberration.

 

When Compact Fleurent bulbs first came out, we had some places where the bulbs glowed dim all night. I tracked it down to several items. A timer, or a dimmer or a ceiling fan speed control. These items need a very small amount of current to keep working. They let some mA of current flow when off. The old bulbs will not light on that small amount of current. One test I did was to take a 4-bulb light that glowed and put one old bulb in. That shunted enough current to keep the other three CF bulbs off.