1 - Place one hand on the wall whilst using
2 - Bosch DMZ-100-Zoom-Thingy-Ma-Bob
Do a search on Ebay, about =A330-35-40-45 from memory some years ago.
How old is the house?
- If it is pre 1960 (and even a little later) it is not uncommon for plaster over doorways to be reinforced with chicken wire where it spans say wood-to-floorboard/joists above. As a result you can get induced voltage and other weird effects.
- Also realise that lighting circuits have a fair distance carrying just Live so can induce voltage.
- Similarly cables running alongside one another can induce voltage via inductive & capacitive effects, put your arm along a cable and you can feel a tingle for this reason and IR testers may complain a circuit is live when it is disconnected at both ends but run alongside several other cables which are loaded.