Hello,

Here's my problem, I have a 2003 f-350 6.0 XL 4 Door, the passenger blinker blinks fast but no light and no brake light on passenger side. Front blinker and mirror blinker works.

I have replaced the MFS, Bulbs, light socket, relay. I have a running light and when you lock it the tail lights up, just no brake light or blinker.

Thanks Larry

 

Sounds like wire short

they blink fast for a broken circuit be it the light bulb or wiring

 

If it's a broken wire, how can the running light work, does the blinker and the brake use the same circuit and the running on it's own?

Thanks!

 

Separate circuits for running and blinker