if all components check good, and everything is properly grounded, the only thing it can be is the circuit is NOT getting power. this means you need to check the wiring closely. even if nothing apparent jumps out [like a blown fuse, or broken wire], you need to confirm if power [12v] is reaching the switch, then leaving the switch to the component[s]. after that, you need to confirm the component[s] is[are] receiving 12v. you may need to run a jumper wire or two, to confirm this. these cars have a very basic system, but electrical issues can be VERY frustrating to solve at times. i REALLY enjoy fixing hack "fixes". []