So I've been searching unsuccessfully for a relay, I'm starting to think that it may not exist. My truck does not have a headlight warning chime that will alert me if I leave my headlights on while my ignition is off. My idea is to use a relay to switch the 12v chime on/off. I want to run power from my headlight fuse to the relay, and also power from my radio fuse (which loses power when the ignition is off) to the relay, so that when BOTH are energized, the chime circuit is open, but if the headlight switch is powered while the radio (accessory) is not powered, it chime circuit is closed. That way, if I turn my ignition off while my headlights are still on, the chime will sound. Does such a relay exist? Or perhaps there's an easier/better way to hook it up. Any thoughts and input would be much appreciated.