I have a 2009 Mustang GT Convertible and recently my left turn signal indicator started to blink twice as fast as normal. I took this to mean a burnt out bulb, sure enough the one bulb was out. the third one counting from the left. I purchased a new buld and replaced it. The new one did not blink either. I exchanged the new bulb with the one in the middle or second position with the new one and it worked fine. Even my old bulb worked in the middle position. The tail light on the right on third position works. Does anyone have any idea what my problem is.

 

I'm guessing it would be a broken wire

 

The wires are good...as sfar as I can see. I will check again to confirm...Thank you for your post.