My left high beam is not working. 2002 C4S. I changed the bulb but it is still not working. I tapped the head light and it worked but then it stopped working. I took the light out of the fender and reinserted it, but still not working. Right side is ok. I checked fuse and it is ok. Any ideas how to diagnose and fix this?
Thanks,

 

I would look at the plugs (male and female) along with the wiring. Is a pin bent on the plug? Look at the bulb socket for any weirdness. Also maybe remove the bulb and use some electric grease on the prongs of the bulb..it helps conductivity.

Just my handful of WAG's

 

As Pete said, it is most likely your connector. Check the headlight side for bent or loose pins, and check the car side to make sure that the connector has not slipped out of the socket.

Also, inspect the wiring inside the headlight for cracked or missing insulation.

 

I had the same problem when I got the car back from a fender accident repair. I released both lights and compared them in the living room and found bent over pins on the faulty light socket. Stood them up via long nose pliers. Put the lights back in the car and all was well. So I would check that part. If you have small hands, you can actually insert the connector as you are returning the lights into the car.