so my passenger light went out, I went to check if it was my bulb or the ballast, I switched my passenger bulb and put it on the driver side and it worked so I was thinking it was the ballast, I had a friend who gave me an extra ballast so I used it and it still didn't work... i then used it on the driver and it worked.. next day later both my headlights don't work... im looking online saying it could either be the fuse or the connectors or wiring harnesses.. anyway how i could find out which is really wrong with it?