2003 S500 turn signal doesn't work
 

The left rear signal doesn't work. I check the bulb and it is OK . I changed the bulb anyway and still doesn't work. I swap the socket from left to right and the socket work fine.Front signal work OK. I check the contact at the socket and it looks fine. Please help. Is there signal flasher? Does to whole tailight wiring ba. I try to move it around just in case the contact got loose but still not work.

It is for 2003 S500.

Thank you

For that I would get the factory electrical diagrams and troubleshoot the problem with a multimeter.

If you don't know how to do that, then take it to someone who can do that for you.

Look closely at the the contact points on the socket and the bulb housing. Overheated, melted, deformed contacts are common.