I spent Saturday adding a pair of cig lighter plugs (basically this) under the dash so that I can 'hardwire' the two GPS units I have. The power goes straight to a Blue Sea fuse block in the engine bay.
By wiring it this way, the plugs are constantly on.
What I would like to do is make the power cut out when a door opens when the vehicle is off (the same way our headlights turn off).
My feeble brain is imagining I can find somewhere to tap into the switch on the driver's door (but how do you keep it off until the ignition comes back on?), or maybe the headlight wire, then run that to a relay.
can you recommend the safest way to do this, and what I might need for a relay? I understand the basics of a relay, but haven't wired any yet