My ex boyfriend installed new headlights last year in my 1999 Jimmy. For a while they seemed to work just fine, but 8 months later they start to flicker at night and early morning. Now they won't come on at all when it's dark. We've tried everything that mechanics had advised. It's not in the switch and no fuses seem to be blown. We thought it could have been the bulbs but they run during the day. We thought it could be the wiring? This is our only source of transportation right now and we have been pulled over and given warnings but no ticket yet and I don't want that to happen. Please help in any way possible.