Not a dome light, a dash light. It's the light that is over your choke and throttle cable knobs. Your manual will show how to wire up the slide switch in order to power up the gauge lights. The gauge lights only light up when the headlight switch is pulled AND the pole switch is in the correct position. You may have an extra wire hanging around not doing anything. That might be the one you need. (use a big mirror for troubleshooting, save your back for the tough stuff!)