Here you have it, number two being the "hardest to find" lower one (Switch EXT1, 10A), for those people with the "high load auxiliary switch panel.
Everybody should have this one in his car, even those with only one battery.
I don't think this was documented before on this forum, and even if it was, well than we have twice the information
View attachment 7818212
How I did? I took a medical injection needle and did put it under an angle in the insulation of the wires, and then connected my multimeter, the one I keep in my car.
[EDITED] only the "live" wire (12V) gets the injection needle, the other multimeter (black) goes to a suitable metal part of the car (ground or negative pole).