Electrical mystery SOLVED

A few months ago we noted a discouraging behavior on one of our 3-way circuits in the kitchen. It seemed that I had somehow mis-wired the circuit such that when one of the lights was burnt out or unscrewed, one of the 3-way switches wouldn’t operate properly. It would turn the lights on/off when the remote switch was in one position, but wouldn’t turn them on/off when the remote switch was in the other position. When we replaced the light bulb it started working again.

This was a total head-scratcher for me. I mean, I know how I wired the circuit and I couldn’t figure out how I would have messed up so badly that a burned out light bulb would affect one position of the switch. I mean, the lights are all wired in parallel so that a burned out bulb wont affect anything else on the circuit.

Then, I was explaining this to my dad when he was here in the spring. He wasn’t understanding what I was explaining so we decided to unscrew the bulb and demonstrate. Well guess what, it didn’t exhibit the wierd behavior - everything worked fine.

Today we noticed that the switch was misbehaving again, only this time there was no burnt out bulb. I flicked the switch a few times and suddenly was surprised to hear a distinct SIZZLE. Whoa! I went down in the basement and turned off the power to the kitchen.

I replaced the switch. Now the circuit works fine. My belief now is that the burnt out bulb was a ruse - that in reality the only problem was a defective switch.

I decided to cut open the switch to see if I could find out what sizzled. Surprisingly I didn’t see much. The plastic on the toggle had a small blackened spot, and one of the two contacts on the inside also showed some blackening. If current wouldn’t flow across this contact properly, that would explain the symtoms we saw.

Assuming the burnt out bulb part of this mystery was indeed a ruse, this mystery is SOLVED. Fingers crossed.