How to Troubleshoot a Defective Electrical Outlet
It is a common occurrence for an electrical wall outlet to stop working or to become defective. Providing you follow the proper safety precautions and that you’re following an orderly logic troubleshooting method, you can solve most of the issues incurring from electrical outlets. This piece will guide you into the proper procedures and how to get through them safely, along with identifying the different types of outlets and their particularities.
Safety Note—Always use extreme caution when working with anything electrical. When working with wiring, always turn off the relevant circuit breakers and test the lines to make sure they're not live. In some places, you may need legal certification to complete advanced electrical projects.
1 - The Different Types of Electrical Outlets.
As you probably already noticed, the electrical 120 volts AC outlets all over your home don’t all look the same, and we’re not talking strictly about style or color. We’re talking instead of types of outlets with unique characteristics, and features to serve very specific needs for different areas of your home—the type used for the bedroom might not be ideal for the bathroom, and the ones around the kitchen counter will also differ in their characteristics and wiring size, even though they all basically provide the same 120 volts source to a receptacle.
A) The 2-prongs, 15 Amps, and 120 volts outlet that has only two identical elongated connection slots were commonly used until the mid-sixties when it became obvious that they created a serious electrocution hazard, not providing the appliances with a protective ground connection.
Although they should be removed from any home, they cannot be simply substituted with the grounded version, as the wiring of that circuit itself doesn’t provide a ground wire, thus requiring a complete rewiring of that circuit.
B) The grounded 3-prong 15 Amps, and 120 volts outlet with a shorter elongated slot for the “Hot” line, a longer one for the “Neutral” line, and a third semi-circular one for the ground wire is the most commonly used outlet around the inside of the house. Its added grounding feature provides an alternate return path for the current, should the neutral return path become compromised.
C) The 20 Amps 125 volts receptacle basically has the same appearance as the 3-prongs 15 Amps, except for a longer slot that is shaped as a sideways “T” letter (see Fig. 1).
Behind appearances, however, its construction is designed to withstand a greater power consumption from an appliance for up to 20 amps without heating up, but must be wired up through a heavier 12 gauge wiring that can withstand the extra load.
Such outlets are better suited for washers, dishwashers, space heaters, around the kitchen counters where you plug-in multiple appliances such as microwave ovens, toasters, etc.
D) Some receptacles are also equipped with a GFCI sensor that constantly monitors the current flow in the circuit, comparing the current flowing through the “Hot” black wire with the current flowing back through the “Neutral” conductor.
When the solid-state circuitry detects a difference of 5 mA (0.005 A) or more between the two lines—created by a leak from the hot line to the ground and known as a ground fault—the receptacle’s sensor activates the “ground trip,” opening the circuit. GFCI and regular receptacles look very much alike except for the two buttons to test and reset the outlet as well as a pilot light showing its status (see Fig. 2).
If a GFCI outlet isn’t working, press the button to reset the receptacle.
E) Another similar type of monitoring receptacle is the “Arc Fault Circuit Interrupter” or AFCI, which—although identical in appearance—should not be confused with GFCIs. AFCIs are engineered for situations where the circuit suffers a sudden short or an unwanted arcing condition in a live circuit.
While both AFCIs and GFCIs are important safety devices, they have different functions—GFCIs address shock hazards, while AFCIs are intended for fire hazards. Unintended arc faults resulting from defective wiring or appliances will cause the circuitry to trip the internal contacts opening the circuit.
Also equipped with a test button and a reset button, the first step to do when the outlet goes dead is to reset it manually.
2 - The Right Testing Device for Troubleshooting.
You should never do electrical troubleshooting on live circuits without a solid background in electrician’s work and knowing all the safe practices and respecting them.
Anyone with basic knowledge of electricity will be tempted to try electrical repairs on their own, but they must never attempt opening live electrical boxes without following those safe practices and safeguards associated with that field or without the proper tools for the job, 2 of which would be the outlet tester and the multi-meter.
3 - Troubleshooting an Opened Circuit
The best tool for troubleshooting the receptacles, and well worth its cost of under $20, is the outlet tester. A particularly worthwhile model is the outlet tester that does double-duty as it incorporates a ground fault circuit tester to check all your GFCI outlets and all the standard receptacles connected to GFCI receptacles around your home (Fig. 3).
If you have an appliance or fixture that doesn’t power up, the first thing to do is to check if the receptacle is a GFCI or AFCI and reset it.
Otherwise, plug in your outlet tester, or if not available, another appliance or lamp in the outlet to eliminate the possibility of a defective appliance. If something else works, the fault is probably with the appliance or device, which is obviously malfunctioning through a damaged electric cord or within its internal electrical circuitry.
If the outlet doesn’t power anything, it is a clear indication that you have:
a) an open circuit that keeps the flow of current downstream
b) a defective circuit breaker that cannot be reset due to internal malfunction, thus keeping it from closing to complete the circuit.
b) or a short circuit that tripped a fuse or a breaker cutting off the current from the whole circuit.
An open circuit can be caused by a loose or damaged wire at or upstream from the affected outlet, possibly from that outlet being internally defective.
Since an open circuit usually has one or both of its lines “opened,” the current cannot get through to any of its components downstream, affecting everything connected to it farther down, so that if you find a defective outlet without power, you need to check every other outlet upstream until you get to one that works.
The problem, therefore, could be anywhere from the outfeed cable of that particular outlet to the next receptacle (that isn’t working), including a break inside the walls between the two.
But electrical outlets are also sometimes wired up with one side of the outlet or even both receptacles controlled by a wall switch. So if you find that you have a defective outlet, you should test both sides of that outlet just to make sure that one of them is not hooked up to a switch, as switching just one side of an outlet is a common enough practice—to power up a lamp for instance.
3.1 - So before going any further with troubleshooting, check the switches around the room to see if one wouldn’t activate the receptacle.
3.2 - If that is not the problem, follow the circuit upstream until you find an operating outlet and make a mental note of which one it is. If none of the outlets is powered, go to section 5 to troubleshoot for a short circuit.
3.3 - When you find a live outlet, locate and switch off the circuit breaker.
3.4 - Remove the outlet cover from the defective outlet to expose its fastening screws, then remove the receptacle from the box giving everything a thorough visual inspection for loose terminal screws, burnt insulation, broken wires, a melted, or a burnt section of the receptacle as in Figure 4.
3.5 - Using long-nose pliers, you should also test for broken wires—from excessive manipulation—inside their insulation jacket.
3.6 - Depending on what your findings are, proceed to do the necessary repairs on the wires or replace the receptacle if damaged.
3.7 - If the inspection and the test came up inconclusive, with the breaker still switched off, move to the previous outlet and repeat steps 3.4 to 3.6.
3.8 - If inspecting this 2nd outlet is also unsuccessful, you have to assume that you have an open line somewhere along the cable inside the walls. You can verify this by disconnecting and shorting out the black and the white wires of this 2nd outlet that feeds into the defective outlet, then taking a resistance reading across both sets of terminals on the defective outlet:
* Zero ohms reading across the terminals where the affected cable is attached indicates that the continuity down through the black wire and back up the white is solid throughout and that the opened connection is probably within the receptacle itself. Replacing the outlet should restore continuity to the rest of the circuit.
* An infinity (∞) reading across both sets of terminals confirms that the cable is defective somewhere between the two outlets and needs to be replaced.
* An infinity (∞) reading across the outfeed set of terminals will again confirm a faulty receptacle.
4 - Troubleshooting a Faulty Circuit Breaker.
Although not extremely common, a faulty or defective circuit breaker that is worn to the point where it can no longer be reset, thus maintaining the circuit open, is still a possibility that should be taken into consideration.
At the main electric panel, if you see that the breaker is actually tripped and while trying to reset it, just can’t get the toggle to catch and stay as it just slips back to the center instead, you know for a fact that there is either a definite short still acting up on that circuit or the breaker has gone bad and is now defective and impossible to re-arm.
The first thing to do then is to confirm the status of the breaker, starting with cutting the power from the panel to avoid any risks of electrocution.
4.1 - Shut off any major current drawing appliances around the house to eliminate a power surge when the power will be turned back on.
4.2 - Set up a battery-operated light shining on the panel.
4.3 - Switch off the main breaker of the panel, cutting the power off to the whole house.
4.4 - Before going any further, with the panel deprived of power, try again to reset the faulty breaker...
* If the breaker does reset and remains “ON,” you still have a short circuit along your circuit, and you need to proceed to section 5 for troubleshooting.
* If the breaker still refuses to stay “armed,” get a replacement breaker of the same type and rating.
4.5 - Remove the cover from the front of the breaker panel to expose the breakers and wiring, and remove the wires going to the breaker’s terminal.
4.6 - Unscrew or pull out the breaker from its bus bar and replace it with a new breaker, securing it in place and then its dedicated wire to the terminal screw.
4.7 - Re-install the front cover onto the electric panel and secure it in place.
4.8 - BEFORE you switch the main breaker back on, switch off every breaker inside the electric panel in order to avoid a power surge throughout the whole house.
4.9 - Turn on the panel’s main breaker and switch on the new breaker to make sure it is working fine. Check all the outlets along the circuit.
4.10 - With the new breaker working fine, turn on all the other breakers one at a time, then close the panel door.
5 - Troubleshooting a Short Circuit
A short circuit usually results in a tripped breaker or blown fuse. While a burnt-out fuse is easy to check by looking through the glass to spot the melted-out link, a tripped breaker will have its toggle sitting loosely with no tension to it, halfway between the “Off” and the “On” position.
The burnt fuse will have to be replaced by another of the same rating, while the circuit breaker can simply be reset by shifting the toggle all the way to the “Off” position and then all the way back to the “On” position until you hear or feel the “click” of the mechanism re-engaging.
As fuse panels are now rarely in use, the descriptions in this piece will refer to “circuit breakers” only, although they’re generally applicable to fuse panels also.
When a short circuit occurs, it’s usually because of a malfunction from an appliance, a device, or simply a loose wire within a circuit or plugged into it, which causes it to draw an unexpected and excessive amount of power.
When such an occurrence happens, the excessive amount of current passing through the circuit breaker causes it to trip and cut the power from any part of that circuit.
If you have an outlet that has no power and while going through step 3.2 you do not find a single working outlet on that circuit, the reason is that either ...
a) the cable or one of the wires is severed between the breaker and the first outlet and therefore leaving the complete circuit without any power,
b) or a short somewhere along that circuit where a loose hot line shorts out with the neutral or the ground wires blowing the fuse or tripping the circuit breaker—depending on whichever system you have.
c) or a defective appliance or device drawing excessive power from a malfunction is plugged into one of the receptacles tripping the breaker.
5.1 - The first step in troubleshooting a short circuit is to reset the circuit breaker.
a) - If the breaker remains on, you can assume that one or more appliances or devices plugged into it—and now turned off or unplugged—caused the circuit to draw excessive amperage, thus tripping the breaker. Check every outlet to find a space heater or some other device that might have triggered the short circuit.
Note 1 - If any such device is going to be used occasionally or on regular basis, you might want to consider adding an extra outlet on a 20 amps circuit to accommodate such demands.
b) - If the breaker cannot be reset or keeps tripping off after you’ve followed the ten steps in section 4, it probably has a short circuit that’s still in play within your circuit that still needs to be addressed.
5.2 - Unplug every appliance in that circuit and try to reset the breaker again.
a) - If doing that did resolve the issue, whatever you had plugged into your circuit that has an amperage rating too high should from now on be plugged into a different outlet on a different circuit breaker, or if it is defective or shorted out, it should be repaired or just simply discarded.
b) - If that didn’t solve the issue, however, you have to assume that the problem is internal within that particular circuit and its wiring. Starting with the closest outlet to the breaker panel, proceed to open every outlet to inspect each one carefully for signs of arcing, melted casings, discolored plastic, and loose wires, also paying attention to burnt smells.
Close attention should also be paid to loose-fitting plugs that are not held with enough tension from the receptacle’s female connector resulting in poor contact.
Note 2 - Once you’ve completed inspecting an outlet, since you’re not finished but need to leave the receptacle pulled out and exposed for further testing, use some electrical tape to wrap around the terminal connectors to keep them from touching anything or anyone.
c) - If your search proves to be conclusive for melted, burnt, or discolored plastic, you should replace the receptacle because of the damage it probably suffered internally. Once replaced, try to reset the breaker again.
5.3 - Testing from the Circuit Breaker to the 1st Outlet.
If the breaker doesn’t reset, go back to that same outlet and disconnect the hot line that comes into the outlet to isolate any short from the circuit, while leaving the neutral and the ground wires connected.
Take a resistance reading across that hot line (disconnected from its terminal) and the neutral and also between hot to ground—you are now actually measuring from the box right up to the circuit breaker inside the main panel, but excluding the receptacle.
a) A zero reading indicates that you definitely have a short between the breaker panel and the outlet box, so the cable needs to be replaced.
Note 3 - Unless you have the necessary experience, you might want to consult an electrician for his professional opinion, however, before ripping anything apart and replacing wiring.
b) If the multi-meter reads “infinity” (or ∞), that part of the circuit is good, and you can proceed to section 5.4.
5.4 - Testing at the 1st Outlet.
At the 1st outlet, disconnect from its terminal the hot line that feeds the rest of the circuit and take a reading across that hot line and neutral.
a) An infinity (∞) reading at this point would indicate that there is no short downstream and that the receptacle itself is defective or shorted out and needs replacement.
b) A zero Ω reading would confirm that the short circuit is still present within the rest of the circuit. Re-connect every wire of that outlet to their respective terminals and re-install the receptacle inside its box.
5.5 - Testing the Remaining Outlets and the Rest of the Circuit.
Go to the next outlet along that circuit and remove the protective tape wrapped around it (from Note 2) and disconnect the hot line that goes to the next outlet, then take a reading across that disconnected hot line and neutral.
a) As in section 5.4b, a zero Ω reading would confirm that the short circuit is still present within the rest of the circuit (downstream). Re-connect every wire of that outlet to their respective terminals and re-install the receptacle inside its box. Proceed to the next outlet and repeat the steps from section 5.5.
b) An infinity (∞) reading at that point, however, would indicate that there is no short circuit downstream, leaving you to test for either a defective receptacle or for the incoming cable being shorted out somewhere inside the walls.
c) Disconnect both hot wires from the outlet and measure across the hot terminals and the neutral terminals. A zero Ω reading would confirm a defective receptacle, while an infinity (∞) reading would again confirm that the receptacle is good and the short circuit probably lies within the incoming cable feed between the last two outlets. That cable will need to be replaced according to the guideline in Note 3.
d) Repeat the steps in section 5.5 until you reach a receptacle with a reading of infinity (∞) downstream or the last outlet.
No matter how difficult or puzzling finding the cause of a dead outlet may seem, the gradual and systematic troubleshooting guide herein will not fail to lead you to the proper diagnosis and solutions. For more help on the subject, check out our pieces on troubleshooting GFCI outlets, repairing outlets, and replacing outlets.