On all three of my MBs the right and left head light are fused seperately. Check your fuses for corrosion. If you haven't done so replace all the fuses and clean the contact points with something like deoxit. These fuses fatigue over time and you can't always tell by looking. For $5 to $10 Put in new ones you'll be amazed at how many germlins this will exorcise

Bob D.