Light with mind of it's own.

[K8MHZ]

Years ago a friend of mine was getting a house he owned ready to rent out so I was helping him make sure all the electrical stuff worked.

I get to the foyer and there is a row of three switches. The foyer light is on. I switched each switch and the light stayed on. So I went hunting for a switch I missed, found none. When I went back to the foyer, the light was off.

So I flipped the switches until the light came on, flipped the switch off and the light stayed on. I stood there and scratched my head a bit and after about 30 seconds, the light went off. I turned the switch on, the light came back on. When I turned the switch off, the light stayed on for 30 seconds or so and then would turn off.

I asked my friend if there was a timer. He said he didn't know, his dad wired the place up and the light has been doing that as long as he can remember. He said he has never seen a timer, even in the basement.

He asked me if I could just make it work like a normal light. I said sure, not really knowing what I was getting into.

I pulled the switch and when I bypassed it, the light would function normally. No 'delayed off' feature at all. If I put the switch back in, the 'delayed off' feature
came back.

So I just had to play with it for a bit. This was a standard on/off switch.

Then I noticed......

When I flipped the switch on, I could hear the click inside the switch. When I flipped it off, there was no click. Until 30 seconds later. The switch would click and the light would go off.

I put a new switch in and all was well. I took the old switch home to play with it.

Sitting on the bench, not connected to anything, I checked it using a meter. I would flip the switch on, hear the click and see the meter respond. I would flip it off and there would be no click for about 30 seconds. Then the switch would make a click noise and the meter would respond to show an open circuit.

I kept that thing around for a while, but have since lost track of it. It was one of the most unique troubleshooting jobs I have run across.

 

[Jraef]

Used to be commonly available. There was a small pneumatic bellows attached to the contacts inside of the switch that provided an Off-Delay operation. When you flipped it on, the bellows was compressed immediately because it had a one-way check valve that allowed full air to pass through, so the contacts closed immediately. But when you flipped it off, there was a smaller orifice in the bellows that only allowed so much air to leak out, giving you a 30 second delay. The idea was to give someone time to get down the stairs when you flipped off the light switch. I'm not sure if anyone still sells them though, they have been replaced by inexpensive electronics now. But the cool thing about the old ones is that they didn't need the Neutral in the switch box to power up any electronics.

 

[K8MHZ]

Used to be commonly available. There was a small pneumatic bellows attached to the contacts inside of the switch that provided an Off-Delay operation. When you flipped it on, the bellows was compressed immediately because it had a one-way check valve that allowed full air to pass through, so the contacts closed immediately. But when you flipped it off, there was a smaller orifice in the bellows that only allowed so much air to leak out, giving you a 30 second delay. The idea was to give someone time to get down the stairs when you flipped off the light switch. I'm not sure if anyone still sells them though, they have been replaced by inexpensive electronics now. But the cool thing about the old ones is that they didn't need the Neutral in the switch box to power up any electronics.

Interesting!! Now I hope I can find the switch to take a look at it. I have never heard of such a switch.