Testing outlet receptacles is an important homeowner skill. It can alert you to possible problems with your outlets; specifically, it can tell you if the grounding pathways are intact and operating correctly. The home grounding is an important safety feature, designed to help channel electricity "to ground" if the case of a short circuit. A properly grounded electrical system is much less likely to cause fires or shocks if a short circuit should occur.
Testing receptacles is also helpful... if you do your own electrical repairs. It will help you determine if the power is off before you work on wiring, and will also verify that you've done repair work correctly.
Depending on the age of your house, your receptacles will be one of two types. Either they will be two-slot polarized outlets, or three slot grounded receptacles. Either type can be tested, and there are a number of small useful tools that can be used to test them:
- Neon circuit tester
- Voltage tester
- Receptacle tester (analyzer)
This article will show how to use the neon circuit tester to test your receptacles for power, reversed wiring, and grounding.
01 of 09
Testing for Power on a Two-slot Polarized Receptacle
When testing a polarized receptacle, first check for power to the receptacle by placing the red lead of the tester in the smaller slot and the black lead into the larger slot. If the tester lights, you have established that the receptacle is powered up and you can continue testing.
02 of 09
Testing for Ground on a Two-Slot Polarized Receptacle
Once you verify that you have power, remove the black lead and touch it to the screw in the center of the cover plate. If the tester lights up or registers, the outlet is grounded and wired correctly. If not, continue to the next test.
Note: if the cover plate screw is thickly covered with paint, the tester may have trouble making contact. Make sure there is a good metal-on-metal connection between the tester probe and the screw.
03 of 09
Testing for Reversed Wiring on a Two-Slot Polarized Receptacle
Place the red test lead into the long slot and the black lead on the center screw of the cover plate. If the tester lights, you have established that the receptacle is wired incorrectly. The hot and neutral wires are reversed and should be switched to make a correct connection. This will normally be a matter of switching the screw terminal connections on the receptacle.
04 of 09
Testing a Two-Slot Polarized Receptacle for Absent Ground
Now try placing the black lead on the screw in the middle of the cover plate and place the red lead in each of the other slots (small and large slots) to see if the tester lights. If it doesn’t light for either, the receptacle isn’t grounded. This is a situation that may require the attention of a professional electrician to troubleshoot and correct.Continue to 5 of 9 below.
05 of 09
Testing a Three-Slot Receptacle for Power
In order to test a three-slot receptacle, check for power between the large and small slot. Place the red lead in the small vertical slot and the black lead into the larger vertical slot. If the test lights, the receptacle is active and functioning correctly.
06 of 09
Testing a Three-slot Receptacle for Ground
Once power is established, place the take the black lead out of the large slot and touch the tip to the center screw on the cover plate. The tester should light if the ground connection is good and the receptacle is connected properly. Now move the tip of the black lead and place it in the round lower slot on the receptacle. The tester should also light in this position. If the tester does not light, there are two possibilities: either the receptacle's wiring is reversed, or there is a... missing ground.
If it doesn’t light, continue to the next test.
07 of 09
Testing a Three-slot Receptacle for Reversed Wiring
Place the red test lead into the long vertical slot and the black lead on the center screw of the cover plate. If the tester lights, you have established that the receptacle is wired incorrectly. Normally the solution in this situation is a fairly easy one: reverse the screw terminal connections on the receptacle.
You can also place the red lead in the small slot and the black lead into the round slot. If the tester lights, this is another verification that the hot and neutral wires are reversed... and should be switched to make a correct connection.
08 of 09
Testing a Three-slot Receptacle for Absent Ground
Now try placing the black lead in the round hole and try placing the red lead in each of the other-other two vertical slots (small and large slots) to see if the tester lights. If it doesn’t light for either, the receptacle isn’t grounded.Continue to 9 of 9 below.
09 of 09
If There is No Power
If there is a case where there is absolutely no power on the receptacle at all, you have another problem. Possible causes include:
- A simple loose connection on the receptacle is interrupting the flow of electricity. Check the receptacle screw terminal connections and make sure they are secure.
- The wiring from the circuit breaker or fuse is damaged and not completing the circuit.
- A circuit breaker has tripped or a fuse has blown. In these cases, you can reset a breaker or replace a fuse if the... circuit looks to have no visible defects.
- A faulty device somewhere along the circuit is causing a short circuit. Try unplugging everything connected to that circuit, reset the breaker or replace the fuse, then one at a time, plug the devices back into the circuit to find the problem, if any.