Fix Light Switch Wiring

Is your light switch not working? Here is the testing method for checking light switches and wiring. © By: Dave Rongey

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Testing Method for Light Switch Wiring
Electrical Problem: I am working on my brothers house to try and help him with his electrical wiring. It is all Romex Type-NM Wire, the house was built in the 198o’s etc.

• The problem is when you push the light switch to on in the bedroom the light switch buzzes and immediately trips the breaker.
• If I reset the breaker all other lights and receptacles work on this circuit as long as the switch to the bedroom lamp is not turned on.
• I removed the light and fan in the bedroom and pulled the switch from the wall and checked the wiring to both. I then disconnected the light completely and moved the wires far apart and capped them.
• I pulled the switch out from the plastic new work box and moved all of the wires away from each other. Hit the switch again and it tripped the breaker. This is where I am unsure.
• Does this mean the short is in the wire from the light switch to the fixture? It appears it is wired straight from the switch into the attic to the fixture. Could any other component in the circuit effect this? If not should I replace the 14/2 from the fixture to the switch?

Thanks for your time. I appreciate it.

This electrical question came from: Greg in Tennessee.

Additional Comments: Very nice website. I read through the trouble shooting and enjoyed it.

Dave’s Reply:
Thanks for your Electrical Repairs Question Greg.

Testing a Light Switch and the Wiring

Greg, there may be a few possibilities that are causing the problem, all of which can be identified using an tester or Ohm Meter.

• Basically, what you need to do is identify each wire set and verify the connections to make sure they are correct.
• If there are two wires from 2-wire cable that are attached to the switch and if these two wires are not connected correctly back at the fixture box then you may be switching a hot and a neutral together and blowing the circuit.
• The other possibility is that a nail has been driven into and across a cable which could be creating a short between a switched leg and the ground wire. Using an ohm meter to check the cable between the switch and the fixture box will reveal exactly what is happening.
• These test should be done with the circuit turned off. This test with the ohm meter is basically a continuity test to verify the cable and see if there is a short between any of the wires, The test should be done with the wires removed from the switch and the light fixture and the wires apart from each other testing wire to wire to see if there is a short.
• If that test proves OK then the test of placing a wire connector with both insulated wires together to see if you have continuity through the two.
• Your basically creating a loop and making sure you have continuity which will verify this.
• Once these tests are made you will no doubt understand more about the circuit wiring and if there is in fact a problem with the wiring which may require you to replace the cable if it is damaged.

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