Things You'll Need
Plug-in voltage tester
Touch-style voltage tester
While receptacles with reverse polarity are not a danger per se to your home, they can damage certain pieces of equipment if they get plugged into the outlet. Anything with a polarized plug (one prong larger than the other) may be damaged if plugged into a reverse polarity outlet.
How to Fix Reverse Polarity Receptacles. OK, so you just purchased your new home and you think everything is great, when all of a sudden the electrical inspector calls to let you know that he forgot to tell you earlier that your electrical outlets have reverse polarity. Oh no! What are you going to do? That's when you stop and think to yourself, what is reverse polarity anyway? All reverse polarity means is that someone connected the wires on one or more of your receptacles incorrectly. Probably a color-blind electrician (yes, they are out there). Anyway, here is how to fix reverse polarity receptacles safely and easily.
Check all of your home's receptacles to see how many of them the color-blind electrician wired. You can do this by using a plug-in type voltage tester. On the tester there will be a chart that will tell you which lights should illuminate when you plug it into a properly wired outlet and what each other light combination indicates.
Once you find the receptacle(s) with reverse polarity, leave the plug-in tester plugged into the receptacle and find the circuit breaker that is delivering the voltage to that line. Turn it OFF. When you return to the receptacle there should be no lights lit up on the tester. If there are, then you turned off the wrong breaker. Try again.
With the power to that circuit OFF, remove the cover plate and the two screws holding the receptacle to the wall box. Gently pull the receptacle out of the box. If there are any other wires inside the box, use a touch-style voltage tester to ensure that they are also OFF. If they are hot, find the circuit breaker feeding them and turn it OFF as well.
Inspect your receptacle. A receptacle with reverse polarity will have the white (neutral) wire screwed to the hot side (copper screw) and the black (feed) wire screwed to the neutral side (silver screw). The bare or green wire should be connected to the green ground screw on the receptacle.
Simply remove the white and black wires and connect them to their properly intended sides of the receptacle. To wire it properly the black gets connected to the dark or copper-colored screw and the white wire gets connected to the silver screw. If the wire looks brittle or damaged, use the wire strippers to cut the old wire away and strip off a 3/4 inch fresh section of insulation.
Wrap a strip of electrical tape around the screw terminals for added safety, resecure the receptacle to the wall box and attach the cover plate.
Plug the plug-in tester into the receptacle and then turn the circuit breakers back on. When you get back to the receptacle the tester should indicate proper wiring. If for whatever reason it still reads reverse polarity, the problem may be in another receptacle or in a junction box somewhere. Your best bet would then be to call a licensed electrician.