I have a 2001 Honda Civic. Recently when I am driving my headlights are really dim but the right one will get bright after a certain acceleration then go back dim. Then they will both turn bright but for a VERY short amount of time. I had the battery and alternator checked and they are both fine. What else could it be?

 

I would suspect wiring issues. First place I would check is the connection between the headlight bulb and the harness. Bad power or bad ground, but other then that I couldn't tell you where to start.

Perhaps RonJ or MK will post... both have a TON of knowledge!

 

+1 on the grounds. That's almost textbook bad grounds with headlights, actually.

I'm not sure where the ground wire for the headlight part of the wiring harness is though.