So why do you want to have power to your dash cam for just a few minutes after you switch off.
When I did mine I had trouble finding normal switched power up in the overhead console as it was all delayed in one form or another. In the end I used a piggy back fuse off the main switch board and ran straight switched power to the overhead console with a cig socket - and used a standard 12v-5v usb plug to provide power.
If you want your dash cam to pick up "problems" while you are away from the car then as Tombie suggested us the correct power kit for your Dash Cam that allows you to do that.
Cheers
Garry

