Submitted by enc-nyc t3_10pdlph in DIY

First time home buyer, never dealt with these things before, but willing to learn. This is pretty old, 1970 era house that has a lot of these older things you won't except to see. Some wiring + power breaker box (which was designed and labeled by someone really special) are frustrating me until today.

One of the first things I've started doing is changing all wall power outlets and light switches. With outlets it appeared pretty straightforward, however I was quite surprised to see that not all outlets have physical ground connection.

With light switches it got even crazier. I am sorry if my issue seems dumb or funny but I have no one else to ask. Here's picture of old + new outlets:

One of the switches in the kitchen here (middle one) was never used by previous owners, they've had a hole in a ceiling instead of the lamp, but we bought a new lamp and obviously wanted to use it. The problem is middle lamp always stays on, if there a bulb in a lamp, no matter what position switch is in. I bought new switches so obviously faulty switches are not an option (besides I tested them afterwards anyway).

In order to get this fixed I purchased a multimeter and made some measurements.

I believe all light switches in the house are operating under some strange inversed logic. Light stays OFF when switch is OFF position (down), but what's interesting, multimeter shows that power is actually flowing from lower to upper terminal (the ones on the right of the switch itself that are supposed to be disconnected when switch is off). It is very strange since as I understood when power flows between these light should be on.

Once switch goes to ON lights goes ON, but power between upper and lower terminals (on the right of every switch) doesn't travel.

I tested this in 3 rooms and it seems that all light switches are working like this throughout whole house.

How is this even possible? Am I understanding something incorrectly?

How do I fix this?



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jkh77 t1_j6jsiql wrote

Hire an electrician


rygon101 t1_j6juycr wrote

You can be scratching your head for weeks on this and potentially make things worse. Best bet is to get it all checked out by a certified electrician. If it's original wiring personally I'd get it all updated.


Engineerofdeath t1_j6juz58 wrote

Sounds like the neutral wire is switched? Instead of the hot wire? Hard to tell based off the picture.


dsdsds t1_j6jv489 wrote

Are you measuring voltage?

When the switch is off, the 2 points will have a voltage difference of 120v. When the switch is on, the 2 points are physically connected, the voltage difference between them is 0.

Look up how to use a multi meter.


Polymathy1 t1_j6jwk8l wrote

It sounds like there is something crosswired.

It also sounds like someone set the switches up to all have power coming into them but then to only switch one leg. Cars do switches like this, where an entire circuit is powered and the switch only changes one connection.

Either way, sounds wrong and dangerous for house wiring. Call an electrician. Could be someone did some goofy wiring and spliced a hot to neutral in the ceiling.


enc-nyc OP t1_j6jxk8h wrote

I did look up. Yes, was measuring a voltage, didn't think it was one line, my mistake.

Thank you.

Now measured a continuity. Seems like everything is working as intended but light is always on anyway.


davethompson413 t1_j6kotxf wrote

Perhaps it's a three pole switch.

Edited to add...and maybe previous owner effectively eliminated this switch from the system. Hence the light is on. OP need to find the other switch.


abdoughnut t1_j6mth95 wrote

The switch works, the wires are the correct ones, then the last owner might have done some weird bypass. Can you show us the wiring more clearly? Try to get a good picture of where they come from and where they go


enc-nyc OP t1_j6n8fqv wrote

I actually (with 2nd switch taken off) put a bulb in a 2nd lamp and it lights up.

Seems like it's hardwired somewhere without even touching the switch. What a nonsense.


enc-nyc OP t1_j6n9bht wrote

No, I've installed a regular one. There's one black cord coming from a 3rd switch that has a opening in the middle. Have no idea what it is for as end of it goes to one of connections of 3rd switch.

2 cords (black and red) should control the 2nd switch I assume.

As a wrote in comment below 2nd light works even with no switch hooked, so it's hardwired somewhere else I guess?


The_cogwheel t1_j6pfw71 wrote

To expand.

Voltage is a relative measurement - think of it as "what is the difference in electrical pressure between these two points".

If you measured two ends of the same wire, no matter what else is happening on that wire, voltage will read close to 0, unless the wire is extremely long (150 ft or longer). Most of the time when we say "oh that's a hot. It's 120v" we're using a reference that is always constant - the ground. Like the literal ground beneath your feet (or the ground wire, which eventually goes into the actual earth outside your home). Because that measurement tells us how likely (and painful) it's gonna be to get a shock from it. More volts = more pressure = more likely and more pain.

When the switch closes (aka in the "on" position), it's the same as having one long chunk of wire rather than two chunk, when it's open (aka in the off position), it's separated agian. So when it's open there is a difference in electrical pressure - one side has 120v (referenced to ground) and the other side has 0v (agian, as referenced to ground) as they are now two separate wires, one with a connection to the panel, the other with a connection to the lights.


The_cogwheel t1_j6pgk26 wrote

Agreed, whatever is going on here is gonna require a professional to probe out and sort. There's likely a bypass or some other weird splice going on, but where and what else is going on with the circuit? Only God knows till someone is able to probe out the whole run.