How to Troubleshoot and Repair Wall Outlet Problems

How do you diagnose and repair a bad wall outlet?

  1. Standard 120V grounded duplex outlets
  2. Swtch-controlled 120V duplex outlets (switch controlls both receptacles)
  3. Switch-controlled 120V duplex outlets (switch controls one receptacle)
  4. Split-circuit duplex outlets
  5. Ground-fault circuit interrupters (GFCI)

The common wall outlet is essentially inert. Current arrives at its hot side and is kept on hold until an appliance is plugged into it, completing the circuit. A standard 15A, 120V grounded duplex outlet has an upper and lower receptacle each with three slots. It is a sturdy and long-lasting device. Any problem can usually be traced to a lamp or appliance plugged into it rather than the outlet itself. When it does wear out or it no longer makes contact with the plug prongs, it can be quickly and inexpensively replaced.

Once the wall plate is removed, you will find one of a number of wiring variations inside an outlet box. The number of cables is determined by the location of the outlet along the circuit. An outlet that is installed mid-circuit (middle-of-the-run) will have two or more cables in the box: One cable coming from the power source and the other going out to the next box on the circuit. An outlet box located at the end of the circuit (end-of-the-run) has a single incoming cable. An outlet is also wired differently if it is controlled by a switch, or if it is supplied by a 240V split circuit.

When connecting the wires, be sure to connect them to the right terminals. Red or black (hot) wires must be attached to the brass terminals (the shorter slot side) and the white (neutral) to the silver terminals (the long slot side). Upper and lower terminals on the same side of the outlet operate as a single unit and may be used interchangeably unless the connecting tab is removed.

In addition to the standard 120V duplex outlet, there is a variety of outlets for special needs. The GFCI (ground-fault circuit interrupter) is an important safety feature required by code in kitchens, bathrooms, garages, and outdoor circuits. It monitors the flow of electricity at an outlet and shuts off all current in the event of a leak.

Heavy-duty 240V outlets, which will accept only matching plugs, are found behind most major appliances. These outlets have to be serviced by a qualified electrician. Both the outlet and its box (if metal) must be grounded to protect against shock in the event of a short circuit. A two-slot 120V outlet will not accept a grounded three-prong plug and should be replaced with a grounded three-slot outlet if there is a grounding wire in the box. Otherwise, replace a two-slot outlet with a GFCI outlet.

When working in an outlet box, use a voltage tester rated for 240 volts and proceed carefully. Work only in dry conditions. Do not touch any terminals or wire ends until you have turned off the power to the outlet and used a voltage tester to confirm that the power is off.

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Duplex outlets

Remove the wall plate: Turn off power to the outlet by removing the fuse or turning the circuit breaker off. Remove the screw(s) on the wall plate and lift it away from the wall. If the wall plate is stuck to the wall with plaster or paint, use a utility knife to carefully cut around its edge. Tape the screw(s) to the plate to avoid losing them.

Free the outlet from the box: Release the outlet from the box by loosening the mounting screws located at the top and bottom of the mounting strap. Grasp the mounting strap and pull the outlet out of the box to expose the wires. Do not touch any wires or terminals until you have tested for voltage.

Identify the wiring: Check the number of cables entering the box. When the outlet is middle-of-the-run, two cables enter the box each with one black, one white, and one grounding wire. The black wires are hot and are connected to the brass terminals (the short slot side). The white wires are neutral and are connected to the silver terminals (the long slot side). When the outlet is end-of-the-run, only one cable containing one black, one white, and one bare grounding wire enters the box. The black wire is attached to the brass terminal and the white wire to the silver terminal. In both cases, a grounding jumper is attached to the grounding terminal on the outlet.

Test for voltage: Use a voltage tester to confirm that the power is off by touching one of the tester probes to the brass terminal where a wire is connected and the other probe to the silver terminal where a wire is connected. If wires are connected to the other set of terminals, repeat the procedure for those two. Then, test between the grounding terminal and the brass and silver terminals in succession. The tester should not show voltage presence in any test. If it does, return to the service panel and turn off the power to the correct circuit.

Service the connections: Check the connections at each terminal. If a wire is loose, rehook it around the terminal and tighten the screw. If the connections appear dirty, detach the wires and clean the terminals and wire ends with fine sandpaper. Or clip the wires and strip the insulation to expose clean wire, then form each wire into a hook and secure it to the terminal screw. Screw the outlet back into the box, turn on the power, and plug a lamp into each receptacle to make sure that the outlet works properly. If the lamp doesn’t work in either receptacle, turn off the power and replace the outlet.

Remove the old outlet: First, make sure that there’s no power to the outlet. Loosen the terminal screws and disconnect the wires.

Install the new outlet: Loosen the terminal screws of the replacement outlet. Hook each black wire around a brass terminal screw and tighten the connections. Then, hook each white wire around a silver terminal and tighten the connections. Connect the grounding jumper (the bare copper wire) to the green grounding terminal on the outlet. Gently fold the wires into the box and set the outlet in place. Screw the mounting strap to the box, making sure that the outlet is straight. Install the wall plate and turn on the power.

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Switch-controlled duplex outlets (switch controls both receptacles)

Remove the outlet: When an outlet controlled by a wall switch is not operating, first check the wall switch. If the problem persists, serve the outlet. Begin by flipping off the switch that controls the outlet, then turn off the power by removing the fuse or turning the circuit breaker off. Remove the wall plate, loosen the mounting strap, and lull the outlet out of the box to expose the wires. Do not touch any terminals or wires until you are sure that there’s no power to the outlet (use a voltage tester to ensure that there’s no power to the circuit).

Identify the wiring: If two cables enter the box, one of the white wires may be attached to a brass terminal; this white wire should be recoded black with electrical tape or black paint to indicate that it is hot. The other white wire is attached to a silver terminal. The black wires are connected with a wire cap. If one cable enters the box, the black wire is attached to a brass terminal and the white wire is attached to a silver terminal.

Test for voltage: Use a voltage tester to confirm that the power is off by touching one of the tester probes to the brass terminal where a wire is connected and the other probe to the silver terminal where a wire is connected. Then, test between the grounding terminal and the brass and silver terminals in succession. The tester should not show any power in any test. If it does, make sure to turn off the power to the correct circuit.

Service the connections: Check the connections at each terminal. If a wire is loose, rehook it around the terminal and tighten the screw. If the connections appear dirty, detach the wires and clean the terminals and wire end with fine sandpaper. Or clip the wires and strip the insulation to expose a clean wire end, then form each wire end into a hook and secure it to the terminal. Screw the outlet back into the box, turn the power on, flip the wall switch on, and plug a lamp into each receptacle. If the lamp doesn’t work in either receptacle, turn off the power, and replace the outlet.

Replacing the outlet: With the power off, remove the old outlet and loosen the terminal screws on the replacement outlet. If there are two cables in the box, hook the white wire with the black marking clockwise around a brass terminal and tighten the connection, then hook the other white wire clockwise around a silver terminal and tighten the connection. If there’s one cable in the box, attach the black wire to a brass terminal and the white wire to a silver terminal. Connect the grounding (bare copper wire) to the green grounding terminal on the outlet. Gently fold the wires to fit in the box and set the outlet in place. Screw the mounting strap onto the box, making sure that the outlet is straight. Install the wall plate and turn the power on.

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Switch-controlled outlets (switch controls one receptacle)

This type of switch-controlled outlet has the link between the brass (hot) terminals removed so both receptacles can be wired independently. One of the receptacles is controlled by a wall switch and the other works like an ordinary outlet. If you see an outlet mounted upside down, it’s probably a switch-controlled outlet. When the outlet doesn’t work correctly, first check the wall switch. If the problem persists, service the outlet.

Remove the outlet: Turn off the power by removing the fuse or turning the circuit breaker off. Remove the wall plate, loosen the mounting strap, and pull the outlet out of the box to expose the wires. Do not touch any terminals or exposed wires until you’ve checked them for voltage.

Identify the wires: If two cables enter the box, the black wires are connected to a jumper that hooks around a brass terminal. One of the white wires is attached to a silver terminal. The other white is attached to a brass terminal; this white wire should be recoded black with electrical tape or black paint, indicating that it is hot. If one cable enters the box, it has two ht wires (one black and one red) to separately deliver power to each receptacle. Both black and red wires are attached to the brass terminals. the white wire is attached to the silver terminal. In both cases, the connecting tab between the brass (hot) terminals has been removed, interrupting the flow of power between the upper and lower receptacles.

Test for voltage: Use a voltage tester to confirm that the power is off by touching one of the tester probes to one brass terminal and the other probe to the silver terminal where the wire is connected. Repeat the procedure keeping one probe attached to the silver terminal and touch the other terminal to the other brass terminal. Then, test between the ground terminal and the brass and silver terminals in succession. The tester should not show any voltage in any of these tests. If it does, make sure to turn the power off to the correct circuit.

Service the connections: Check the connections at the terminals. If a wire is loose, rehook it around the terminal and tighten the screw. If the connections appear dirty, detach the wires and clean the terminals and wire ends with fine sandpaper. Or, clip the wires and strip the insulation to expose the wire ends. Then, form a hook to each wire end and attach them to the terminals. Screw the outlet back into the box, turn the power on, plug a lamp into each receptacle and play with the switch. If it doesn’t work, replace the outlet (assuming that the switch is OK).

Installing the new outlet: Confirm that the power is off. To ensure that the two receptacles of the new outlet will operate independently, use long-nose pliers or a screwdriver to snap off the connecting tab between the brass terminals (short slot side). Do not snap off the tab between the silver terminals. If there are two cables in the box, hook the white wire with the black marking around one of the brass terminals and the jumper from the pigtail of black wires around the other terminal and tighten the connections. Connect the white wire to a silver terminal. If there is one cable in the box, attach the black wire to one brass terminal, the red wire to the other brass terminal, and the white wire to a silver terminal. Connect the grounding jumper to the green grounding terminal on the outlet. Screw the outlet in the box, install the wall plate, and turn the power on.

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Split-circuit duplex outlets

Remove the outlet: On a split-circuit duplex outlet, the upper and lower receptacles of the outlet operate independently, each connected to half of a dedicated 120/240V circuit. Commonly found in kitchens, the split-circuit duplex provides power to appliances, such as toasters, electric kettles, and coffeemakers, which consume a great deal of electricity. When the outlet is not operating correctly, turn off the power to the 120/240V circuit at the main service panel. Unscrew the wall plate, loosen the mounting strap, and pull the outlet from the box to expose the wire connections. Do not touch any exposed wires or terminals until you make sure that there’s no power to the outlet.

Identify the wiring: One cable enters the box (one black and one red), each attached to a brass terminal (the short slot side). The white wire is attached to a silver terminal. The connecting tab between the brass terminals has been removed, interrupting the power between the upper and lower brass receptacles.

Test for voltage: Use a voltage tester to confirm that the power is off by touching one of the tester probes to a brass terminal and the other to the silver terminal where a wire is connected. Repeat the procedure for the same silver terminal and the other brass terminal, then between the two brass terminals. Test between the grounding terminal and the brass and silver terminals in succession. The tester should not show any voltage. If it does, return to the service panel and turn off the power to the correct circuit.

Service the connections: Check the connections at the terminals. If a wire is loose, rehook it around the terminal and tighten the screw. If the connections appear dirty, detach the wires and clean the terminals and wire ends with fine sandpaper. Or clip the wires and strip the insulation to expose clean wire ends, then form the wire ends into hooks and secure each wire clockwise on its terminal. Screw the outlet back in the box, turn on the power, and test the outlet. If the outlet still doesn’t work, Turn off the power, disconnect the outlet and install a new one.

Installing the new outlet: Confirm that the power is off. To ensure that the upper and lower receptacles operate independently, use long-nose pliers or a screwdriver to snap off the connecting tab between the brass terminals (the short slot side). Do not snap off the tab between the silver terminals. Attach the black wire to one brass terminal, the red wire to the other brass terminal, and the white wire(s) to the silver terminal(s). Connect the grounding jumper to the gree grounding terminal on the outlet. Gently fold the wires into the box, screw the mounting strap onto the box, install the wall plate, and turn the power on.

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Ground-fault circuit interrupters (GFCI)

Test the outlet: The GFCI outlet protects the circuit and you by tripping instantly when it detects a leak in current. Code requires that GFCI outlets be installed in new and remodeled bathrooms, kitchens, garages, and outdoor places. They are also recommended in workshops, laundry rooms, and other damp locations. To ensure continued protection, check the GFCI outlet every month by pressing the ‘TEST‘ button. If the ‘RESET‘ button doesn’t pop out, service the outlet. When a GFCI is not delivering power to an appliance, the fault could be with the appliance or the outlet. Unplug the appliance and press the ‘RESET‘ button. If the GFCI still doesn’t work, go to the next step.

Identify the wiring: Turn off the power to the outlet by removing the fuse or turning the circuit breaker off. Remove the wall plate, loosen the mounting strap, and pull the outlet out of the box, taking care not to touch any exposed wires or terminals. if two cables enter the box, each of the black wires is connected to a brass terminal and each of the white wires is connected to a silver terminal. If one cable enters the box, the black wire is connected to the brass terminal marked LINE and the white wire is connected to the opposite silver terminal. Some GFCI outlets have leads in place of terminals: two white, two black, and one green grounding lead.

Test for voltage: Use a voltage tester to confirm that the power is off by touching one of the tester probes to the brass terminal where a wire is connected and the other probe to the silver terminal where a wire is connected. If there are wires connected to the other set of terminals, repeat the procedure for these. Then, test between the grounding terminal and the brass and silver terminals in succession. The tester should not show any voltage in any test. If it does, return to the service panel and turn off the power to the correct circuit.

Service the connections: Check the connections at the terminals. If a wire is loose, rehook it around the terminal and tighten the screw. If the connections appear dirty, detach the wires and clean the terminals and wire ends with fine sandpaper. Or clip the wires and strip the insulation to expose the clean wire ends. Then, form the wire ends into hooks and secure each wire clockwise to its terminal. Screw the outlet back into the box, turn on the power, and press the RESET button. If the outlet still doesn’t work, turn off the power, free the outlet from the box, and go to the next step.

Replacing the GFCI outlet: If there are two cables in the box, tag the wires to help you when reconnecting the new outlet. Wrap masking tape around the black and white wires connected to the LINE terminals. Disconnect the outlet. If there are two cables entering the box, hook the tagged black wire around the brass terminal marked LINE, and connect the tagged white wire to the opposite silver terminal. Then, connect the second black wire to the second brass terminal and the second white wire to the second silver terminal. If there’s one cable in the box, attach the black wire to the brass terminal marked LINE and the white wire to the opposite silver terminal. Connect the grounding jumper to the green grounding terminal on the outlet. Gently fold the wires back into the box and screw the outlet back into the box. Install the wall plate, turn on the power, and press the RESET button. If the GFCI outlet still doesn’t work and there are two cables in the box, a faulty appliance or connection at another point along the circuit may be causing the GFCI to trip. Check the other boxes along the same circuit.

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