300sdl no low beam headlights

I am having problems with my headlight low beams, At first the right low beam worked intermittanly now neither will work. Both bulbs are good.All fuses in main box check ok.
Is this a dimmer switch,headlight relay, poor connection in harness,
any ideas. Thanks Ron

Of course, I'm sure you've tried to replace a bulb in good condition and is suitable for your car. I also assume you've checked and cleaned the contacts may Connection chassis harness connectors for the headlights.