[plain OM]

Thanks so much! To confirm, the arrows in your last pic are the power wire that's paired with the coax wire in the connector at the amp?

Yes.

 

[huesmann]

OK, looks like I gotta pop off the side trim and check voltage at that connector with the radio on.

 

[1 Lucky Texan]

What radar said - Gen3 cars were all plagued with broken wires in the hatch boot.

 

[huesmann]

Coming back to tell how this was resolved.

I figured I needed a guaranteed switched 12V supply to the red ringed wire, rather than taking any chances on other wires in the rear hatch area. I tapped into the red ringed wire above the hatch, then ran a wire up to the front, through the rubber gaiter, along the wagon window, down the trim beside the rear seat, along the plastic panels at the door sills, up the driver's side kick panel, up along the panel below the steering wheel, and into the panel covering the shifter (manual trans), tapping into the cigarette lighter power wire.