Well, many feel more comfortable running two separate wires to their lights and that's fine. Me, I run a good quality wiring harness and be sure to clean the area behind the mounting areas for the lights on the inside of hood. There is a steel backing plate for the headlights that snugs up to the metal there when lights are fastened, and the hood and plate need to make a good electrical connection -i.e. bare metal is best -no painted surfaces or crud buildup. Then, the headlight 1/2-20 hex nut and lockwasher will guarantee a good connection once tightened down. I have never had a problem with my lights using the original one-wire harness method of connecting and I have used my 8N for many night time projects either mowing grass, plowing or discing a field, or plowing snow, and my lights have never failed me. To each his own. As mentioned, you can first try to test the lights to be sure they are not burnt out. Remove bezel, take out lamp, connect wires/test leads from battery to each lamp terminal. Illumination will determine that it is good. Not typically likely you get both lights burning out at the same time UNLESS -you have a 12V battery and are using 6V lamps---so, without this information, I have given you just about all I can offer. FYI -6V sealed bean lamps -p/n 4019...12V sealed beam lamps -p/n 4419.
Tim 'PloughNman' Daley(MI)