Problem with Light Switch Wiring

By Dave Rongey Summary: Electrical Troubleshooting Question: I just purchased a house and notice that the wash room light switch is in the corner inside the room, approximately 6' away from the door.

How to Fix a Light Switch Wiring Problem

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Electrical Troubleshooting Question:
I just purchased a house and notice that the wash room light switch is in the corner inside the room, approximately 6' away from the door. The electrical service panel is about 12 feet away from the light switch. I decided to move the switch closer to the door.
It looked simple enough, so I did. I had some metal jacket 12-3. The wiring in the switch is 14-2.
This is a problem but not my question. I moved the switch to the door and the light was working fine, even though I had not grounded it yet. When the ground wire or bare wire was being connected while the switch was on, the breaker tripped. I tried to reset it and it would not reset. Not my question.
Everything in the house was working prior to this event.
Now nothing works except the air-handler and it is in the off position.
The only way to cut it off is to turn the unit maintenance switch off or the breaker.
The thermostat is in the off position.
Did I just screw up all the wiring in my house?
Thanks- Tim.

Hi Tim - Great Electrical Repair Question!
No I do not believe you just screwed up all the wiring in your house.
You may have caused a control module to go bad when the light circuit shorted and went to ground.

First of all I must stress that you should shut off the power to your circuit before you do any modifications to the wiring because you need to do some electrical troubleshooting.
What appears to have happened is that the ground wire shorted to an energized screw terminal of the switch or one of the wiring components and caused the fault. If the breaker did not reset it could be because the fault needs to be discovered and repaired. I would recommend that the ground system and all the bonding be checked and verified.
With a correct wiring installation the electrical service is bonded to an approved grounding method which includes bonding all the circuits for one complete and functioning system which originates at the main electrical service.
When a fault occurs it should not affect anything else IF the grounded system is completely bonded. Because the air handler system has been affected by the short which occurred with the light circuit this would cause me to question the ground and bonding system.

A thorough inspection of the bonded grounding system should begin at the main electrical panel looking for loose ground wires or even ground wires that were cut off and not bonded at all.
Aside from the ground system, each electrical circuit that is installed correctly should function without disrupting any of the other circuits of the panel with few exceptions.
Sometimes a fault could cause the main breaker of the service to trip, but this is rare. When something like this occurs its is a good idea to work your problem backwards. In other words, what happened last right before the problem occurred.
Find out what that was, and either find out what was done wrong and correct it, or just remove what was done and go back to the way it was when it used to work normally.
Usually when you are going through the sequence of events something is discovered that was not right. If you do not discover a problem then I would suggest making a wiring diagram and draw out what the circuit should be.
Once you have an understanding of the logic of the circuit then proceed. If something does not make sense then do some research to become familiar with the circuit and its components. and let me know if I can assist you further.
Be Careful - Be Safe - Never work on energized circuits!