71 duster headlight issue

X3 for the dimmer switch if you are just fixing by guesses.
Educated guessing also it’s all 50 years old . Even if it works it’s need replacing for being trustworthy. Why I’ve replaced alt , starter , battery and all cables , wiper motor , heater motor ignition resistor & silver box thing I don’t know what it is , and points cap and wires and plugs and bulbs around the entire car.