Strange problem with voltage / light

Look for the doorbell transformer in the electrical box and disconnect it. An electrician won’t help here, I would say, he only measures everything through to assign every burning point etc. to every circuit. That takes hours or days and therefore costs you a lot of money, you can do that yourself...

Sorry, it took me a few days. The problem still exists, unfortunately I haven’t made any progress. I got a 12V LED bulb as a test and connected it, but even that doesn’t work. I’m at my wit’s end. Also strange: no matter whether I toggle the light switches (or turn them off), the 12V voltage remains. Normally, shouldn’t the voltage go to 0 when the light switch is turned off, or not?

You didn’t drill any holes?

Yes, we drilled holes in the ceiling of the adjacent room for curtain rods, but I didn’t notice anything there while drilling.

that could definitely be related to the doorbell. when I read 6V/12V, I immediately thought of the doorbell transformer. Either measure through and get to the bottom of it. If you’re not a professional, please have an electrician take a look.

What exactly does “measure through” mean? I measure 12V with my measuring device on the lamp cable. When I turn off the doorbell transformer fuse, nothing changes either.

From what year is the entire electrical system?

I can’t say exactly. Something has been done repeatedly, you can tell by the age of the sockets, for example. I guess the electrical system in this room is from the 60s or 70s.

At how many points can you switch on the lamp in the hallway (how many light switches are there)?

Once on the ground floor at the beginning of the stairs, then right next to the lamp on the upper floor, and then again at the end of the stairs in the attic, so there are three light switches.

Look for the doorbell transformer in the electrical box and disconnect it.

An electrician won’t help here, I would say, he only measures everything through to assign every burning spot etc. to each circuit. That takes hours or days and will cost you a lot of money, you can do it yourself...

I turned off the fuse, but unfortunately nothing changes :-(

Best regards and many thanks for all the answers Marius

Well then: remove all fuses, really all of them, and measure at the questionable lamp outlet. If the voltage disappears, then gradually put the circuits back into operation until your strange voltage returns there. Then switch everything off again except for the one questionable circuit and see what is still connected to this circuit: sockets, permanently wired kitchen appliances, etc., etc., to first find out where the cable leads and where it might still pass by.

My guess was just a (defective?) light switch for the push-button circuit.

Your 6 or 12 volts come from somewhere else, induction or something else. If many cables lie close together somewhere, you will never measure zero volts. But as soon as you connect a load, it collapses. That’s why your 12-volt LED won’t light up. I believe it might be related to your doorbell. Maybe even 230 volts ran over there. Who knows what electrical work has happened there in the 110 years and who messed around with what and where. I myself have already seen a garden shed completely wired with 230 volts and doorbell wire....