Any electricians in the house??

OK, this is a new one for me. I've always done my own electrical work, but this one has me stumped.

Has anyone ever heard of an electrical wall switch failure like this?

We have outdoor LED string lights that are activated by a regular wall switch mounted in a weathertight enclosure.

Noticed tonight that the string lights were on but at a very dim setting with the switch off. They havent been on in a couple weeks.

Broke out my fluke meter.

-Switch on: 120V downstream of switch
-Switch off: 112V downstream of switch
-120V upstream of switch regardless of position.
-Switch is less than a year old and feels fine with positive click for on/off

WTF is going on here, any ideas?

I have the power to that circuit switched off and will replace the swtich tomorrow, but that's an odd duck failure IMO.

This book helped save me a few times when I still owned a 1940s NJ home with mostly 1940s electrical wiring and had to deal with unexplained "electrical gremlins".

Your Old Wiring 1st Edition
by David E. Shapiro (Author)

https://m.media-amazon.com/images/I/..._AC_SY780_.jpg

Is the ground okay? Dimly on when switch is off sounds like bad ground. That's just a guess.

Also check out minimum load. I don't entirely understand this, but if the minimum load for a switch to function doesn't match (is higher than I think) the minimum load of the LED, then the LED dimly illuminates. It meant we couldn't use a really cool designer switch in our kitchen because there was a "minimum load mismatch" with the LED overhead lights.

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Originally Posted by j44ke

Is the ground okay? Dimly on when switch is off sounds like bad ground. That's just a guess.

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I was going to suggest checking the neutral (because I think of electrical wiring in terms of old homes that may not have ground wires) but my armchair-electrician days are over.

It sounds like the switch has a "welded contact". When you turn the switch to the off position the contacts are staying partially closed. This can happen when a circuit is overloaded and is much more common with contacts on a relay, but obviously can happen with a switch as well. When you replace the switch it's worth verifying that the "hot" leg is being switched and not the neutral. I've seen that before, and it can cause some strange issues. LED lighting can also be very particular about voltage. Some are dimmable and some are not. I've seen LED light fixtures constantly flash on and off like a disco light when wired to a dimmer.

Quote:

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Originally Posted by AngryScientist

OK, this is a new one for me. I've always done my own electrical work, but this one has me stumped.

Has anyone ever heard of an electrical wall switch failure like this?

We have outdoor LED string lights that are activated by a regular wall switch mounted in a weathertight enclosure.

Noticed tonight that the string lights were on but at a very dim setting with the switch off. They havent been on in a couple weeks.

Broke out my fluke meter.

-Switch on: 120V downstream of switch
-Switch off: 112V downstream of switch
-120V upstream of switch regardless of position.
-Switch is less than a year old and feels fine with positive click for on/off

WTF is going on here, any ideas?

I have the power to that circuit switched off and will replace the swtich tomorrow, but that's an odd duck failure IMO.

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Is it a digital dimmer switch?

mystery solved. cracked the bottom screw to the box and about half a gallon of rusty looking water poured out of the box. examining the switch itself, shaking it produced water out all crevices.

obviously the weather tight box was not tight enough. new box, new switch, everything works now.

Today's learning, when replacing GFCI outlets don't assume just because your replacing a
Levtion with a Leviton the wiring is the same.

Old Leviton, line on the bottom terminals, new Leviton line on the top terminals.
I didn't know Italians engineers worked for Leviton.