I changed the driver's side headlight after the bulb burned out on my W163, then two days later the passenger's side was out. So I went ahead and changed the bulb as well. Now the headlights on both sides are not shinning at the same angle. I looked to see if I need to make adjustment to the headlights but did not see where I can do that. I thought I inserted one of the bulbs in wrong but the bulb only goes in one way. Now I am really confused. I did not do anything but pulled the bad bulb out and put a new one in. What causes headlights not shining at the same angle? Will replacing one bulb cause the other to fail or you have to replace both at the same time even one is out and the other is not?

87 W124
95 R129
98 W163