Tried using a non-contact voltage tester on a circuit I thought was dead in an old Baltimore row house, and it didn't beep even though the line was still hot.

Turns out the tester was picking up interference from the knob and tube running parallel in the wall, so now I always double-check with my meter before I touch anything in those pre-war places, has anyone else had a similar false negative happen?

3 comments

3 Comments

patricia_gonzalez21d ago

My 1920s place does that too, always check with the meter.

ellis.faith21d ago

My old tester did that near a transformer once.

milarodriguez21d ago

Actually @ellis.faith, that was probably a magnetic field tricking the sensor, not the transformer itself. Non-contact testers pick up stray voltage from wiring all the time. It's a common false positive that makes people think something is live when it's not. Those little testers are NOT reliable for safety. You really need to check with a proper meter that measures actual voltage.