routing through the ACC key position should be good, better through ON position, use a relay to keep the switch contacts free of any extra load, A great way would be to intercept the main current line at the headlamp switch and route it through relay contacts 30 and 87, the key can provide positive to contact 86 and contact 85 goes to ground.

voila - great circuit to cut off the headlamps when you key off the engine.

I loved my VW Golf for this, the key on position also carried positive supply to the headlamp switch. It also had a load reduction relay that cut off power to nearly all items on the car, headlamps, A/C blower, rad fan and stereo for full juice supply to the starter.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)