PC9-416 Audi A3 06-09 Fully Active Amp Wiring Harness Adaptor RCA to Quadlock. A harness adaptor lead allows you to install a car radio of your choice with out cutting any of the existing car wiring. All harness adaptor Leads are ISO ended and will plug directly into most models of car radio. To activate speakers, the blue & White wire also needs to be connected to the Blue wire coming off of the New Head Unit (marked Amp Remote). For fully amplified vehicles.