Expert: Mike Evans - 8/31/2009

Question
I own a 1996 BMW 318i.  I have a brake light that went out.  I replaced the bulb, but the light is still out.  I thought a fuse may have blown, but after replacing the fuse, I found that that the problem doesn't lie with the bulb or fuse.  I have no clue what's causing this malfunction. I checked the connections to the bulb to see if they were corroded, but they are clean.  I'm at a lose.  Can you help me diagnose the problem?

Answer
    If it's just one bulb, then it's one of two things.  Either you put in the wrong bulb (you have to check the number on the old bulb or in the owner's manual) or the socket has become damaged.  Most European cars have the sockets and bulbs accessed through the trunk.  If you carry something heavy around and it whacks into the taillamp housing during acceleration, it will probably break something.  In my case, it was my bowling bag with 16lb. ball.  Sometimes the sockets just go bad from corrosion or whatever and you have to replace them.  You will probably want to look into the socket to see if it's messed up, then start working back through the harness with a voltmeter to find out where the break is.