12v at light switch

[Ohmslaw]

Just wondering why there would be 12v showing on my meter when I put my tester across my cables at the light switch?

The room only has 1 light switch, but wired as a 2 way with both L1 and L2 being used. I've disconnected everything, and between L1 and L2 I get 12v, between common and L2 I get 240v, and common and L1 I get 12v.

This indicates to me L2 is actually common, but just wondering why the hell there is a cable in L1, and why the 12v?

 

[winston1]

Electromagnetic induction and a high impedance meter.

 

[EFLImpudence]

This indicates to me L2 is actually common, but just wondering why the hell there is a cable in L1, and why the 12v?

Common does not mean live. It is the switch terminal which connects alternately with L1 and L2 when the switch is operated.

In your method of two way switcing, it is not the Common which is the supply Live.

In another method it is.

 

[Ohmslaw]

Cheers for info. I know about electromagnet induction, but cant remember it showing 12v before (been a while)

Just puzzled me as I only have the 1 light switch but this 1 switch is wired as it being 2 way. My only other thought is they have just just put the neutral into L1 rather than a connector, and switch wire into Common.

Could prove this by going to light or board, but was lazy and wanted to see if there was an easy explanation before I went and did it!

 

[Taylortwocities]

My only other thought is they have just just put the neutral into L1 rather than a connector, and switch wire into Common.

There is no neutral connected at the switch.
Look at the schematics. Can you spot where the neutral is connected?

 

[Ohmslaw]

There is no neutral connected at the switch.
Look at the schematics. Can you spot where the neutral is connected?

I know theres not meant to be a neutral, but cant think why else there another core there.

 

[Taylortwocities]

There may be a hidden/blanked off switch somewhere. I’ve seen several examples of this where rooms have been altered over the years.
Can’t say for sure without being there with a test meter.

 

[aptsys]

Electromagnetic induction and a high impedance meter.

Unlikely to be induction - the mutual inductance between those cables and another carrying enough current to induce a voltage into it to measure with a DMM is not hugely realistic. Much more likely to be capacitive coupling.

 

[Ohmslaw]

Unlikely to be induction - the mutual inductance between those cables and another carrying enough current to induce a voltage into it to measure with a DMM is not hugely realistic. Much more likely to be capacitive coupling.

Is this normal at a light switch?

 

[Ohmslaw]

Actually opened up a switch in a different room, and the same wiring and the same voltages is there - even though it's still just 1 light switch in the room

 

[Ohmslaw]

This is the wiring (wires closest). This one is a 3 gang

 

[Ohmslaw]

So in this case, when light is on, Common and L1 I get 12v. C and L2 I get just continuity, and L1 and L2 12v.

When light is off, C and L1 I get continuity. C and L2 i get 240v, and L1 and L2 I get 240v

 

[Taylortwocities]

When testing voltages like that, you should be testing between EARTH (or neutral) and the various cables.
There’s no knowing what you’ll find in other cases.
For instance. If you test between one of the L terminals and the COM, you may be measuring from a live conductor, to the switched live, through the lamp and on to neutral.
Look at the diagrams and try and understand what you are prodding.

 

[Ohmslaw]

Cheers for help, appreciated