If you know for sure the bulbs and fuses are good, it has to be either the switch or wiring. Look at the connector that goes to the light assembly in the engine bay. Pin 3 on each one should be your low beam power and pin 4 should be the high beam power. Use a voltmeter and check to see that you are getting power to each pin.

If that is good, re-connect the connector, and then unplug the headlights themselves and check for power there. If you do not have power there, the problem is bad somewhere between the headlight plug and the connector in the engine bay.

Good luck!

Glenn

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2012 Mercedes ML350 Bluetec 102K (hers)
2005 Corvette 55K (fun car)
2002 VW Jetta TDI 238K (mine)
1998 Volvo S70 T5 Turbo 211K (kids)
1994 Ford F150 4WD 246K (firewood hauler)
1983 Mercedes 300D 384K (diesel commuter)