One headlight brighter than the other - what gives?

[ismellburning]

Following my bizarrely popular thread on dead headlights (five pages on one-eyed cars, anyone?) the other thing I'm seeing a lot of at the mo is cars with two headlights, one of which is *way* brighter than the other. Both headlights work, but one is apparently on full-beam while the other's normal. Absolutely blinding, of course, and I would think quite hard to diagnose from inside the stricken car.

So this is a two-part head-scratcher:

1. How on Earth does this happen? The lights can't be getting different amounts of voltage to them, can they? Could a decent bang knock a headlight out of alignment?

2. How do you check that your car isn't suffering from the same effect? Standing in front of my car the only thing I could diagnose is that, yes, both of my headlights are blindingly bright.

GO. Oh, and drive carefully in the snow.

[Palms]

Probably knocked his/her headlight out of alignment whilst changing a bulb OR the bulb is on its way out

[Ozzie Osmond]

Lousy adjustment. If your car is like that, the fix is easy. You don't need any fancy equipment,

• Find a large flat area facing a vertical wall. Multi-storey car park is ideal.
• Drive the car right up to the wall; headlights on full beam; mark each beam centre on the wall.
• Reverse the car back in a straight line - beam centres should stay on the marks you made.
• If one beam has drifted off its mark, adjust it to hit the mark.

Job done!

[Mr2Mike]

IME this is mainly due to people being incapable of fitting new lamps correctly into the holders. Still have to give them some credit for not just driving around with one headlamp working, as so many seem to.