Unexpected voltage measured - explanation?

Small correction, it was of course not a transformer, but an AC/DC power supply. The power supply says 230V +-15%. That is probably the reason why it works, even if the voltage is somewhat outside the 15% tolerance. What ulterior motives? I want to do exactly what I described - without ulterior motives.

Small correction, it was of course not a transformer, but an AC/DC power supply.
On the power supply it says 230V +-15%. That is probably the reason why it works, even if the voltage is somewhat outside the 15% tolerance.
What ulterior motives? I want to do exactly what I described - without any ulterior motives.

I already understood that, but what for? :D

Who says that I am a layman.

No one says that, it is an assumption triggered by your questions. I would stay away from the device and tap a switched positive for turning on the fan from a safely operated power supply.

Sure, I am not a master electrician – if that makes me a layman, so be it. However, I am capable of completely renewing the electrical system of an apartment as part of a full renovation, including the conversion from classic neutral wiring to TN-C-S. I know how to use crimping pliers and a multimeter. The electrical system of a car with countless non-standard modifications is also no problem. OK, I didn’t know about the Steinmetz connection – shame? I would at least somewhat claim that I mostly know what I am doing. There is no need to tell me things like "Electricity is deadly." Water is also deadly if you can’t swim. To the point: The reason for the whole intended setup can be found here: In short: To prevent moisture (and thus mold) from forming behind a refrigerator placed at an exterior corner in the future, fans are to be installed in the ventilation grille at the base below the fridge to promote air exchange behind and beside the appliance. For this purpose, five 8cm PC fans are to be installed side by side to cover the entire cutout in the base. However, these are not to run continuously but to be switched on from time to time. Hence the idea: the refrigerator’s compressor switches on from time to time – that could be utilized. Flat connector spade taps were quickly crimped, but then the surprise with the 270 V. Hence this thread.

As said. Take the power for the power supply from a socket and use a switched positive for the fans. It is better to control this via a humidity sensor than via the compressor.

I could do that, a control using a Raspberry Pi was already considered. But then the thought came up that it doesn't have to be more complicated than absolutely necessary. And the existing regular switching of the compressor was convenient - which would additionally have the nice side effect that the noise disturbance from the fans and the compressor only occurs simultaneously and otherwise there is quiet. I wouldn't know any other (simple) construction that could precisely replicate that.

What exactly is the basis for your discouragement of my idea? That you don't trust me to properly tap the correct terminals, or that the applied 270V shouldn't/can't be used from a technical point of view.