as if the button had been pushed. I've ruled out loose wires and all sorts of jiggling.
When a solenoid is switched off (either with a transistor or with a relay) a high voltage is produced.Wiring nearby could pick that up, e.g a sensitive PIR sensor with unshielded wires.Start with connecting a diode (e.g. a 1N4004) across (and close to) the solenoid.Cathode towards 12volt, so the diode does not conduct during normal operation.It might not fix the problem, but you need it anyway.Leo..
Start with connecting a diode (e.g. a 1N4004) across (and close to) the solenoid.
1N4007 is fine.Leo..
but something disconnected is just crazy.