You made sure the bulbs are not burnt out?
Check for power at the red/black wire at the multi-function switch. Make sure the red w/yellow wire at the multi-function switch is grounding. The last thing is to check for continuity between the two pins on the switch that those two wires go to. There should be with the switch in the low beam position. If there is no continuity and the power and grounds check out than the multi-function switch is probably bad.