As you have found , the supplied 'mount' is crap.
Even the holes do not line up ..it is just an off cut of stainless steel..utter shit..but the lights are good.
No idea about the yellow wire
But yes, the CA goes down and that is correct..the power is coming through the shunt on the bike, and the CA displays current flowing through the shunt. it probably reads about 0.25 ?
edit , just thought, does your CA have the separate speed sensor, the magnet sensor on the front wheel and not pick up the speed from the hub.
if o then that wire is probably the pulse sender for speed if you ditched the remote sender and used the speed sending from the hall pulses
Mongoose frame, Fox F100 forks,26x2.3 tyres
100V 20Ah LiPo
Lyen 18 FET 65 Amp,5304 in 26 inch Mavic rim
To illustrate the vain conceit that the universe must be somehow pre-ordained for us, because we are so well-suited to live in it, he mimed a wonderfully funny imitation of a puddle of water, fitting itself snugly into a depression in the ground, the depression uncannily being exactly the same shape as the puddle."
-- Richard Dawkins, in "Lament for Douglas" (14 May 2001)