Electrical Question

[Warhammer]

This is for a light switch that mysteriously stopped working (goes to a ceiling fan with 4 lights).

If I check the voltage on the live leg (switch off), I show 120V, across the neutral I show 0V. So far so good, when I flip the switch I show 120V coming in, but only 114V on the neutral.

So does this mean the switch is bad?
I should be seeing no drop across the switch, the drop should be at the load, right?

[JonInMiddleGA]

I'm pretty sure I have no clue wtf you even just said lol

(carry on, just laughing at myself there)

[Warhammer]

Update: The switch was bad, apparently was bad for a while, the lights were noticeably lighter with the new switch.

[PilotMan]

Learning has occurred.

Maybe.

[CU Tiger]

The "neutral" (grounded conductor) is never ever ever connected to a light switch.
That's not how it works.

You should read 120v across an open (off) switch, and 0 volts actors a closed (on) light switch.

If you were measuring to ground instead of across the switch, then your language would make sense. But still 114 is plenty to run a light. The switch should pass full voltage through with zero drop, but 114 volts would be indiscernable.

Sorry I've been to a dinner party and enjoyed some well aged bourbon...if this isn't helpful I'll clarify tomorrow. But I'm afraid you may have a hazardous situation there.

[NobodyHere]

"You may have a hazardous situation, but we'll talk about it tomorrow."

I'm sure Warhammer will sleep well tonight

[Warhammer]

That was due to my incorrect terminology. I was measuring everything to ground. I was calling the outgoing wire the neutral.

I am with you 114V should be plenty to run the fan and lights. The only thing I can figure out is if there is a safety in there to prevent running with insufficient voltage, but that should be set to a value of less than 108V.

[CU Tiger]

Sorry for my poor wording last night. Was a bit foggy headed


Ive never encountered a fixture with a safety shut down in it, and honestly cant imagine why such a thing would be designed in. A light bulb would simply put out a dimmer light and an electric motor would spin at a (slightly) slower speed. No real electronics that would be voltage sensitive.


There are two potentials I'd be concerned about given your initial info.
Some of this thought is home age dependent.

1- Id want to make sure there isnt a fatigue break in the wire near the switch screw. Can be common from improper bending of the "hook". Can be hidden by the insulation and not apparently visible. I see this semi frequently. As long as the 2 "broke pieces" are near each other the current just bridges the miniscule gap and flows on. Everything can work but its a heat builder and can end in fire.
2- Similar concept but Id want to make sure there isnt a loss of insulation integrity where the wire enters the switch box and there is some current bleed.


I guess a 3rd one occurred to em while I was typing. i am assuming that all switches are hard landed and you dont have a mickey mouse electrician that has used the back stabs. If they are stabbed in the back, Id fix that first.

[Warhammer]

Originally Posted by CU Tiger

Sorry for my poor wording last night. Was a bit foggy headed


Ive never encountered a fixture with a safety shut down in it, and honestly cant imagine why such a thing would be designed in. A light bulb would simply put out a dimmer light and an electric motor would spin at a (slightly) slower speed. No real electronics that would be voltage sensitive.


There are two potentials I'd be concerned about given your initial info.
Some of this thought is home age dependent.

1- Id want to make sure there isnt a fatigue break in the wire near the switch screw. Can be common from improper bending of the "hook". Can be hidden by the insulation and not apparently visible. I see this semi frequently. As long as the 2 "broke pieces" are near each other the current just bridges the miniscule gap and flows on. Everything can work but its a heat builder and can end in fire.
2- Similar concept but Id want to make sure there isnt a loss of insulation integrity where the wire enters the switch box and there is some current bleed.


I guess a 3rd one occurred to em while I was typing. i am assuming that all switches are hard landed and you dont have a mickey mouse electrician that has used the back stabs. If they are stabbed in the back, Id fix that first.

There were no fatigue breaks. I did not check for insulation breaks. I did check voltages after the new switch was installed and the in and out were the same.

EDIT: I realize I am much more familiar with industrial systems, it blows my mind that things worked at 120V, but not 114V. Most lines coming in are not "clean" so most devices are able to operate with a +/-10% voltage with no ill effects.

[CU Tiger]

Originally Posted by Warhammer

There were no fatigue breaks. I did not check for insulation breaks. I did check voltages after the new switch was installed and the in and out were the same.

EDIT: I realize I am much more familiar with industrial systems, it blows my mind that things worked at 120V, but not 114V. Most lines coming in are not "clean" so most devices are able to operate with a +/-10% voltage with no ill effects.

I'm with you. I spent 10 years doing high end and high volume resi and the last 8 now doing industrial power systems. Frankly in Charlotte Metro it was rare to see within 5% on 240V at the meter base. Ive seen as low as 181 service delivery voltage. Duke Power (now Duke Energy) said anything over 75% of nominal is considered "normal and acceptable". Thats why I was shocked that you were seeing it not work on 114V.


Something in my gut says you still havent found the real culprit, and the manipulating of the wires cause a better connection somehow. But Im anal like that.


Of course if you have (it ounds like you do) a decent multimeter you should be able to ohm out the old switch and test resistance through the closed contacts and maybe gain some insight