I just hooked up an Alpine head unit to a 280W amp in the trunk designed to power a sub. I have 13V at the + on the amp straight from the battery, yet I cant get the amp light to come on and show power. The fuse is fine in the amp. Do I have the cables messed up? My head unit has three preouts ... rears, fronts and sub-w. Which should I use? Do I need to wire the "remote" wire out of the head unit? Any thoughts?

That would be my guess. The amp needs a trigger to turn it on.

...and of course, the amp needs to have a good ground from it's - terminal as well, same guage as the + power wire.

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1986 560SL
2002 Toyota Camry
1993 Lexus