The other day a friend called me to tell me that he installed an electrical light switch to his outdoor shed’s flood light so he could switch it off from inside the house. It turned the light on and off, but when it rained, the light would glow – even with the switch off! He thought – incorrectly – that it was installed correctly because the light went on and off with the switch. I told him it was a shock hazard, possibly an electrocution hazard and to turn the breaker off until I could check it out for him (and don’t let his dog near the light pole!).
The problem that I found was that the switch was installed into the white neutral wire circuit rather than the black hot circuit wire. When he turned the switch off, the electricity still ran all the way out to the shed light and back, but stopped at the switch. The light couldn’t go on unless there was another path to neutral or ground. The is a very dangerous circumstance that could result in a person getting shocked or electrocuted.
The fix was simple enough. Take the switch out of the neutral wire path and place it properly in the hot circuit (usually black) wire. Once that was done and the circuit breaker was turned back on, everything worked safely as it was supposed to.
So why did the lamp glow only when it rained? Any guesses out there?
See my next post for the answer.