I own a 2006 mustang. LH inboard signal light was out. I replaced the bulb, still not working. Plugged the new into the outboard socket and it worked. Put the bulb from the outboard socket (was Working) into the inboard socket and it didn't work. I can plug either bulb into either socket and they will work but I can't get both bulbs to work at the same time.

What's up with that?

Thanks for any help, Jim

 

From your description, the inboard socket is bad or the wiring for the inboard socket. Time to whip out a multi-meter and start poking around. Good luck...

 

Problem solved. Even though they have the same physical and electric specifications and even though they work one by one, You can't use bulbs with different numbers. I bought two new 4057's and the signal works. (This is probably something everybody knew except me.)