How to Repair a Circuit that Stopped Working

By Dave Rongey - Summary:

Electric Circuit Has Power But Does Not Work: How to Troubleshoot 120 volt Circuit Wiring.

Electric Circuit Repair

Electrical Question: The lights in my guest bathroom and the fan in that bathroom suddenly stopped working.

First of all, I consider myself a good handyman and know a lot of basic plumbing and electrical facts. I may give you tons of facts mainly because the rest of the internet has asked very basic questions.
Bathroom Electrical Problem

  • House is 15 years old.
  • There has never been any electrical changes.
  • The wiring is tight, the bulbs were tight, the bulbs have been changed, both switches have been replaced with new bulbs.
  • The circuit breaker never tripped.
  • At the switches, the voltage reading from black to ground is 120volts.
  • The wire coming to the light fixture shows 120 volts from black to ground.
  • The electrical box is plastic.
  • Only these 2 items on this circuit are having trouble.
  • The problem happened during a party. They worked fine before the party.
  • At the time they stopped working, every light in the house was on and also kept working after.

That’s about all I can give at this point.
Any help or direction is appreciated.

This electrical wiring question came from Chuck, in Gold Canyon, Arizona.

Additional Comments: Awesome!Thanks very much for having this web site.

Dave’s Reply:
Thanks for your electrical wiring question Chuck, and your kind comments about the website.

Electric Circuit Has Power But Does Not Work

Application: Troubleshooting and Testing Electrical Circuit Wiring.
Skill Level: Intermediate to Advanced.
Tools Required: Basic Electricians Pouch Hand Tools and Voltage Tester or Continuity Tester.
Estimated Time: Depends on experience and level of problem solving skills.
Precaution: Testing live wires is dangerous and should be done by an experienced individual only. Testing using a continuity tester should only be made after the circuit has been identified and turned OFF and Tagged.

How to Troubleshoot Circuit Wiring for a Bathroom Light and Exhaust Fan

The Missing Element of a 120 Volt Circuit

  • Chuck, It appears that the circuit wiring that leads to the bathroom light and exhaust fan has lost connection to the neutral.
  • From what you have described, there may have been several lights that were on during the party, which may have contributed to a deteriorating condition of a spliced neutral wire up in the junction box of a ceiling light fixture.
  • Flush mounted ceiling light fixtures that use incandescent light bulbs create heat which extends up into the electrical junction box of the light fixture. Over time, heat can cause the insulation of the wiring to become brittle and crack, and the expansion and contraction of the heat of the fixture and the circuit wiring can create a deteriorated condition which can eventually lead to a faulty splice.
  • This is very common with neutral wires and high resistance electrical loads. I would begin by checking the wiring of the light fixtures that are closest to the bathroom and inspect the wire splices, paying close attention to the neutral wires.

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