I guess I don't need a headlight harness...

[Klutch9]

I finally got around to measuring the voltage drop of the headlight circuit in my Sedona. My battery was putting out around 14.24 V at idle, and voltage at the bulb was 14.21 V at idle. Not too shabby! I still may upgrade to an H9 bulb from the H11B, we'll see.

 

[Colt45ws]

Thats really good, but did you check the using the bulb ground or engine ground?
I ask because some of those systems are ground-switched. meaning the bulbs have Pos(+) at all times and the ground runs into the switch or lighting controller. There would be your voltage drop.
You can simply measure from the bulb ground to the engine ground and any voltage shown is your voltage drop.