Dec 242011

Question by Toivo L: Why would power to a circuit be interrupted when screwing in a light bulb?
I recently had the light fixture off to painting a ceiling. I accidentally hit the wires together and caused a pop and spark, but it did not trip the circuit breaker. When I re-installed the fixture it no longer worked. I use a voltage detector and there is power flowing into the box, but when I screw in a light bulb, there no longer is any power flowing in.

What could cause this and how could I detect and fix it?
We have tried two different fixtures, so we know the fixture is ok. We have also tried multiple bulbs.

Best answer:

Answer by Ralfcoder
You may have:

damaged the fixture

broke the filament in the light bulb

reconnected everything incorrectly.

What do you think? Answer below!

  6 Responses to “Why would power to a circuit be interrupted when screwing in a light bulb?”

  1. you need to check all the breakers, or at least reset them. just because there isn’t an arrow pointing to the tripped breaker doesn’t mean it’s not tripped.

    power doesn’t “flow”, btw.

  2. # 1 verify the circuit did not trip, there may be more than 1 circuit in the box so double check.
    Your o’k if there is power at the switch.
    # 2 Make sure you put the wires back the way you found them. Black to black, white to white.
    # 3 I hope you did’nt have a dimmer, because a short can blow a dimmer.
    After that not sure.

  3. You probably have a loose connection some where. When you short out wire it can cause loose connections to happen somewhere else in the circuit. When this happens sometimes the wires are close enough to carry a little voltage, but not enough to carry any current. The same is true about a wire that is broken but still touching. I would check the connections on that circuit. Also if you are using a “hot stick” or non contact voltage detector and reading voltage you may have lost a neutral. A good way to check and see if you have lost a neutral is to connect the hot like normal, then connect the fixture neutral to the equipment ground temporarily. If the light works you have lost a neutral, so you must find the problem. Never leave an equipment ground carrying current, It is dangerous!

  4. recheck the breakers.

  5. Your voltage detector is reading what we call phantom voltage. When you install a bulb, it is absorbed by the bulb, but is not enough to light it. Check your circuit breaker again. Turn it off and then back on. Then check for open or loose connections in the hot wire caused by the short circuit. A short like that can make a poor connection fail, like what you are describing. Voltage detectors have their place, but electricians use a meter for trouble shooting.

  6. You could have lost your neutral connection. If your voltage detector is one of those neon lamps, you probably don’t see a phantom voltage – but measuring across a good light bulb that has no neutral, you’ll “see” the same voltage on both sides of the lamp, and the neon detector won’t light. Good luck finding the break!

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