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Spooky Fluorescent Lights

My home is 8 years old. I live in Michigan. I have a good deal of home improvement experience but limited in many respects.

My question: I have an electrical circuit in my basement that I installed for lighting. Of the eight, 4 foot shop lights on the circuit, two of them flicker faintly when the switch is off. Each of the lights are associated with an electrical outlet. These two lights are clearly getting some residual electricity when the circuit should be dead. What is the problem?

If you have the time to consider my question, I would be grateful for a reply.

Thanks
Terry


There is something strange going on in your wiring. Does your house show any other signs of being haunted?

Just kidding. But to have fluorescent lights flicker when the power is OFF is quite weird. I have never heard of this problem, but there must be a logical explanation.

I would start by getting a good electrical tester. I recommend two actually. First, a "non-contact" electrical tester is handy because you never have to touch any bare wires. It looks like a fat pen with no ink tip. You press the "clip" to activate it, and it beeps repeatedly when placed close to a hot wire.

I also recommend a decent-quality digital multi-meter. I have seen these as low as $30. Necessary features are AC volts, DC volts (for cars, cordless tools, and such) and Ohms (resistance) function.

My approach would be to get inside the light fixture. You might want to turn off the breaker while doing this. 

Remove the plastic cover, if any, remove the bulbs, remove the metal cover that protects the wiring. Then replace the bulbs, you can't test much without the bulbs present.

With the supply wires exposed, restore the power. With the switch off, check for power at/near the hot (black) wires that supply the ballast. The ballast is a black box-shaped device with wires running to it. Some fixtures have separate transformers and capacitors (starters).

My suspicion is that someone wired the switch so the NEUTRAL wire is being switched. (This would be a code violation) If there was voltage present on the black wires, even when the switch was off, then there might be enough of an electric field to partially energize the fluorescent light.

In fact... just turning off the breaker to the light fixtures may give you some clues. If the problem goes away with the circuit dead, then my #1 suspicion still stands. Otherwise, consider these other possibilities:

- Faulty switch may not be fully opening.
- Is a dimmer switch used? There are special dimmers for fluorescent lights. I have seen regular dimmers leak a small amount of power.
- Is there a GFI receptacle upstream in the line? I have seen GFI's act weird, like trip when I touched the ground wire.
- Is there a large wire near the affected lights? Current in wires generates magnetic fields, which may be picked up by the transformer that is built into the ballast.
- Is there a high powered radio transmitter nearby? It's a dumb question but I gotta ask....

Strong electric fields can supposedly make fluorescent bulbs light up... with no wires at all! Supposedly you can take a fluorescent bulb and hold it vertically while standing under those very-high-multi-KiloVolt power lines... and the bulb will glow! Supposedly. But I've never done it.

Please reply when you find out something... I'm dying to know what is going on.

 

Bruce W. Maki, Editor.


( Terry later replied that the switch was indeed on the neutral line instead of the hot line.)

 

 

 

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Compiled June 12, 2001