Good to know you have some skills in electronics, you'll need them !
Having your headlights on when opening the doors from a distance is IMO a pretty good idea, but the realisation will not be as easy a "pull an extra wire".
Your signal source will be the interior courtesy light, this one is powered under certain circumstances, one being door opening (or unlocking), being from the door itself or from the remote.
First problem is you don't want your courtesy ON when driving at night.
Second is the courtesy is driven by the BCM, its output is probably too low for the heads.
First can be solved by using a relay, power from head will not flow-back to courtesy when relay is open.
Second would be solved by the same relay IF the BCM can sustain the relay coil (need a flywheel diode anyway).
So far so good ? NO !
There is a third issue: the ON and OFF proccess are dimmed (voltage is ramping) ! The relay might find it hard when around its switching voltage. To avoid any trouble, one should use a Schmitt trigger circuit, being of discretes or integrated doesn't matter, as soon as it present a high impedance at its input (power from the BCM) and its output is relay driving capable...
One could thing about using the original relay (in the engine bay connection box), but this one is earth driven, while the BCM output to courtesy is positive :-( .
So defo need an intermediate "thing", being a relay or the schmitt trigger !
BRs, Bernie
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