The system works on grounds to turn lights on. The light switch grounds the headlight relay which grounds the wire to the dimmer switch. Problem is bad relay or break in the fuse box between brown/yellow and white/black wires. Try grounding each of these wires, headlights should start working if all fuses are good etc. Check connectors also.
Wayne Samel
August 2007
Common problem, Check all the connectors and fuse pins under left side dash.