Reversed Polarity
Hot and neutral wired to the wrong terminals on an outlet. Devices still work, which is the trap: their switches and shells stay energized when "off."
Polarity exists so that switches, fuses and the threaded shell of a lamp socket all live on the hot side: switch off, and the device is genuinely dead. Reverse the wires and everything still runs, but the lamp socket shell is live with the switch off, toaster elements stay hot at the first touch of a knife, and "off" means "waiting." It is a classic finding on DIY outlet swaps where black and white met the wrong screws.
The three-light tester catches it instantly, which makes reversed polarity one of the few wiring faults homeowners can fully detect themselves. Testing every outlet after buying an older home, or after any handyman-grade work, takes twenty minutes and regularly finds a few.
Talking to a contractor about this?
Run the project past a licensed electrical pro first. Calls are answered around the clock and routed to a pro serving your area.
- Ground Wire (Equipment Ground) : The bare or green wire that carries no current in normal use.
- Grounding Rod (Grounding Electrode) : The 8-foot copper-clad rod driven into the soil near your meter, connecting your electrical system to the earth itself.
- Bonding : Connecting all the metal parts that could become energized (panels, pipes, pool equipment, gas lines) so they sit at the same voltage and faults trip breakers instead of waiting for a person.
- Bootleg Ground : A jumper from the neutral screw to the ground screw inside an outlet box, installed to fool testers into showing "grounded.