Have you checked the fuses in the engine bay? Not got any audio at the minute so I can't tell if anything is working or not that doesnt involve a moving part or a light!
hi.. looks like earth.. so under battery tray are few earth kables screwerd to chasis legs.. clean them with sandpaper to bare metal and stick them back to and you can spray some white grease over top of them....
next /it this dont help / go check fuse box in right hand side of car/ is under front panel....there are fuses for fan, heater...