Connecting into the accessory

[bcf5016]

Hi! I am trying to figure out how to connect accessories (e.g. whip lights) into the accessory of my bike.

I actually was able to connect the whip light to the front light red julet connector (using a 48v to 12v inverter).

Then, I tried to wire the whip light into the 7-pin accessory connector under the seat, but it looks like whenever I try to connect the inverter to the red and black wires in the 7-pin accessory, the voltage drops down to 0.4v or something nominal (vs 12v expected coming out of the inverter).

I suspect that there is some sort of limiter to prevent a short on the draw from the accessory.

Does anyone have a diagram of the 7-pin julet connector that powers the accessory ports? I can't seem to find anything. Would prefer to tap into the accessory vs cutting into the system on the bike.