I have a 2003 Honda Civic. After replacing my right head light, my high and low beams were out of sych. On low beams, my left head light was on low beam and my right head light was on high beam. On high beams, my left head light was on high beam and my right head light was on low beam. My mechanic does not mess with the electrical system. Does anybody know what the problem could be?

 

Do you have HIDs installed?

 

if the headlight wiring was never tampered with then its probably a defective bulb.

easy way to find out is to try a new bulb or try swapping the bulb with the left side and see if the left high and low beam are now backwards....
another way you can confirm that its not a wiring issue is with a multi meter or a test light. you check both left and right sockets for power and make sure the same terminals are getting power with high beam, and check again with low beam on..this will confirm that the wiring is ok and it is actually a defective bulb....but its much easier to just swap the bulb from left to right

the only other possibility i can think of is if the headlight bulb socket was replaced on the right side, then who ever replaced it mixed up some wires...or possibly the terminals got pulled out of the socket and someone stuck them back in the wrong spot.