Two questions...

First: Currently I haven one 12W7 running with the JL 500/1 and sometimes it fades in and out (hits harder then softer) I keep hearing this could be because when it was installed the ground wiring wasn't done right?

Second: I am in the process of putting in another W7 with 2 alpine MR 1000 and a secondary battery.....different alternator needed??

Car is a 2006 ford explorer