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How to Troubleshoot Electrical Wiring Problems


For Electricians or Qualified Technicians: Methods for troubleshooting electrical problems for outlets, lights or switches that do not work, lost power to an electric circuit in a room.
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How To Troubleshoot Electrical Problems

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Understand that not all electrical problems are going to be related. My experience when troubleshooting electrical wiring has revealed that some electrical problems can be attributed to human error.

Other failures occur due to faulty or incorrect wiring that eventually goes bad, then there are times when electrical equipment or devices fail because of bad connections which may be aggravated by environmental conditions such as moisture.

My primary goal of this web site is to help people understand what is involved with the home electrical systems so we don't have to end up troubleshooting your house electrical wiring problems. Usually there is a logical reason why an electrical failure has occurred.

Identifying Home Electrical Problems and Electrical Wiring Failures

Here is a simple formula for Troubleshooting Home Electrical Wiring that will help solve your electrical problem:
electrical-wiring troubleshooting

I must admit that my father loved troubleshooting! He would rather take on the task of troubleshooting electrical wiring then he would construction jobs, he was the Best Troubleshooter there was; and I'm glad to say that I listened and paid attention to his teachings about troubleshooting. Many times it pays to be quiet and just observe.

Ask questions - then Listen, and the pieces to the puzzle start to appear.

Quick Checks just to make sure:
Is the Switch "On"?
Is the Light Bulb burned out?
Is a GFI Receptacle or GFCI Breaker tripped?
Is a Circuit Breaker tripped or a Fuse blown - If so find out why!

Sometimes troubleshooting is easy and extremely obvious - like a switch that was forgotten about or yes - the darn light bulb was just burnt out. You may even discover that a GFCI receptacle or breaker was tripped. There have been times when the tripped GFCI Plug was behind a pile of boxes in the garage and no one ever knew there was a plug there.
Well, I could go on and on with stories about troubleshooting electrical wiring, but lets get to a method that could save you a lot of time, frustration and a bunch of money.

The method I've learned is an easy one, and you've probably already used it several times on other applications, here it is:
The Process of Elimination Which Starts With Identification

Safety First
Be sure not to work with energized wires or circuits.
Identify the circuit and shut it off, then tag the circuit to keep it off.
Before testing, make sure to cap your wires with wire nuts or insulate them with electrical tape when you need to turn the circuit back on. Identify the Hot wire coming in with Red or Black electrical tape so you can identify this wire from all the others. This is what I call "flagging the hot wire"

Very Important:
If you don't feel comfortable working on your electrical problem, please don't take chances - call a professional electrician.

Here is the process
Make sure to identify which cable provides the power coming in.
Do not work on the circuit with the power on. Turn the power off and label the circuit so others know you are working on it.

Positively identify all the cables - what cable goes where.
Check all devices served by each cable. Disconnect any devices that may be connected to any associated cable. Check these devices to see if they are malfunctioning. Isolate or remove any device in order to eliminate a failing component.

Is a Switch involved? - Check the switch with an OHM Meter.
Is it a fixture that doesn't work? Safely test the fixture with a spare cord to see if it works. If it does not - check the fixture wiring, bulbs etc.

Neutral Wires
Be careful when testing neutral wires, because a neutral wire can produce an electric shock if the circuit is energized and a load is on the circuit..
Sometimes a circuit hot wire will test ok to a grounded path such as a water facet, or typically a ground wire, but will not test ok to the white neutral wire. This can be caused by a few things, most of all a loose or burnt wire connection that has burnt to the extent of a lost connection. This may occur at a screw terminal on a receptacle outlet, or the push-in insertion point on the back of a receptacle outlet. Without the neutral wire connection a device will not work. Be sure to check all the neutral connections at the power source, and at any junction leading to the problem area.

electrical plug burnt neutral A Warning about Space Heaters:

Some high wattage space heaters used over a period of time can cause a receptacle to become over heated, especially on the neutral side.

If a receptacle becomes discolored where the cord is plugged in then chances are the wiring attached to the receptacle inside the receptacle box will have experienced over heating and could possibly be burnt.

Make sure these receptacle circuits are turned off before removing the cover plate and receptacle for inspection.
electrical plug burnt hot

Checking The Wire Connections

Make sure your connections are well made. A loose connection will also cause shorts and create burnt wires which could result in a potential fire hazard.

Twist wires together using pliers before screwing on any wire nuts, this ensures a good connection. Don't over tighten wire nuts, but make sure they are on tight.

As the circuit and all the components are checked you should identify the problem. Most of the time it is something very obvious.

Let me know if this helps you,
I really enjoy your comments and suggestions!

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Be Very Careful and Be Safe!

Learn about Safety and the Importance of Electrical Testers:
Click Here to learn more about Voltage Testers

More about Electrical Troubleshooting

Learn more about troubleshooting electrical wiring

More About: Troubleshooting Electrical Problems


Troubleshooting Old Electrical Wiring

I Came in to help a friend. Old existing 12 gauge wire, appears it goes directly to the panel and a 20 amp breaker. I wired up some GFI outlets(1st time, but sure its right), light on outlet comes on, 220V showing on my meter, plugged in fan, nothing. The breaker at panel does not trip. Working on other wiring in the attic, I noticed some of the same old wiring had been cut out, (small pieces under staple). Any idea? Of course I'd rather replace the wiring entirely, but low pitch of roof and drywall is up. Feeling dumb, Thank You for your time.

Hi Jason, first off - if you are in the USA you should not have 220 volts to the GFI Outlet. This alone could be an indication that there are problems with the wiring that needs immediate attention. You mentioned that you are helping a friend, so I am curious about what the original problem was that needed assistance? You are right in mentioning that it would be best to remove and replace the old wiring, and make any corrections as needed to make the home safe. The home owner should consider having a professional electrical wiring upgrade.

Electrical Circuit Troubleshooting

I have a circuit that is out. We were sitting down watching TV when our dining room ceiling fan/light flickered and went out. The line comes up from the electrical box to a bedroom, and that ceiling light works, but everything from there out does not, yet the switches and ceiling lights have power. We tested them with a meter and they all beeped showing there was power going to them. The only weird thing that happened is after the lights went out a couple of days later a smoke detector that is hard wired to the same line started going off. It would give a couple of beeps, then speed up and beep loudly and after a few seconds the beeping continued but the sound level would get much quieter. We had to disconnect it to stop it-none of the other detectors went off (not hard wired)and we checked for any sign of fire-there was none. Help! Any ideas? Why would the lines show power going to them if the fixtures do not work?
M Smith,

From what you have explained I believe that the circuit has lost connection with either the power or the neutral source. This may be found be at one of the device boxes, such as an outlet or light fixture. This would explain why there is an abnormal voltage reading, but devices are not getting full power, which is most likely a result of power that is feeding back through the wiring and devices from other locations.

Appliance Testing

I was trying to electrically test and tag a food processor without success. The item was not marked as being double insulated, so I made the assumption it was type one. The item was fully sealed so I was unable to attach the probe to exposed metal. Any advice?

Tim, you may need to reference your common test lead to the termination point of the ground, or attach to the ground at the power source.

Questions about Why a Home has Lost Power

Question from Jeff, in Belfair, Washington:

Why has part of my house lost power?

We lost power to the area due to storm. When the power came back on we could not get lights to two bedrooms and the bathroom, plus several outlets. My brother pulled a breaker and tested it with another breaker, and he replaced the breaker, now we tested the line wires the white wire if grounded makes the light come on plus all the outlets but get nothing. When a GFI is installed back in the box I get nothing with the tester. When I jump it with a tester white to black, only when I test the white wire to the bare ground wire. There are three Romex wires into the box, and light switch about six inches away. What am I missing? I hope I said enough for you to help me. Thank you for your time and consideration.

Dave’s Answer:

Local Electric Utility Company

Jeff, This sounds like the electrical service from the main utility is only providing partial power. This may be due to a transformer problem, or other damage that occurred from the storm. Call your local electrical utility provider and describe the lost power condition, and request that they send a repairman who can test the main electrical service to your home.

Question from David in Lone Grove, Oklahoma:

When I operate my oven my lights come on, what is causing this?

I came home today, my refrigerator and electricity in the front 2 bedrooms of my trailer house works, but nowhere else. I can turn the burners or the oven on and my lights will come on, I turn stove off and the lights go off. I unplugged the stove thinking there might be a short in it, but guess not.

Dave’s Answer:

David, One portion of the electrical service is faulty, and this is causing a voltage feedback condition. This is a serious condition that will require troubleshooting the electrical power and service panel, and then making the appropriate repairs by a qualified electrician.

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