I try to connect my A518 OD activating by means of switch

no
I believe power goes to the center pin.Then each of the others is grounded thru the switchs. This is what I have been told.
So in your drawing, the yellow wire should receive 12v power, and the pink should run to one switch, while the dark wire should run to the other. And then on each of those snap-switches, the second pin goes to ground.
The yellow supply wire should come from the ignition run circuit. That's the small-gauge blue wire under the hood, at the ballast resistor.. You can also pull run power out of the fuse box. Or my favorite, run it off a battery powered relay, triggered from the run circuit.
Check out Trailbeasts garage, maybe his set-up is shown there.