im sorry but it isnt the alt charge wires, i ran a std 55amp alt on my tdi powering twin optimas that supplied power to twin 8274's with no hassle
mrht can back me on that.
get that earth direct back to the batterys and im sure it will cure it
ive got twin gp winches front and rear, and i forgot to refit the earth lead to the front winch on the last outing, which lead to it not being able to bugger all until i refitted it
however the back worked fine
i remember years ago u kept getting hassle with my rear huskey with, that also turned out to be poor earth's. the chassis just aint good enough really as you have got 4 points of contact before it hits the battery rather than two good points when going direct