2014 Ford Fiesta Car Audio Installation Instructions 2014 Ford Fiesta Car Audio Installation Instructions. Car Radio Battery Constant 12V+ Wire: Yellow/Red. Car Radio Accessory Switched 12V+ Wire: Run a primary wire to your steering column and use the violet/green wire in the ignition switch harness. This violet/green wire will provide you with a switched power source. 2014 Ford Fiesta OE Wiring Harnesses & Stereo Adapters Ford Fiesta 2014, Factory Replacement Wiring Harness by Metra®, with OEM Radio Plug. For factory stereo. This high-quality Metra wiring harness is just what you need to replace your defective or aged factory wiring harness. Ford Wiring Harnesses - Car Audio Stereo - Car Subwoofers Are you in the process of replacing your Ford factory radio with an after-market car stereo? Avoid having to cut OE plugs and making a mess of it all! Our Ford wiring harnesses can help you perform a clean installation without hassle.