Left blinker doesnt blink, but works as running light
 

2003 B3000
295,000 miles

Blinker on dash started blinking fast recently. I just swapped my bulbs out, assuming that was it. The amber film was feeling off of them anyway. But with the new bulbs, the left front blinker still wouldn't work as a blinker. It comes on when I turn on my headlights or running lights. It just won't blink.

Am I pretty solid looking at a wiring/grounding issue? Something easier I haven't checked?

The left rear blinker works fine

Ford uses a Brown wire for all the Park lights

Front Left turn signal uses Light Green/white stripe wire in 2003, but............

The front turn and Dash indicator turn bulbs are on one circuit and the rear left turn/brake are on another circuit, so they are separate, which is why rear can work and front doesn't or visa versa

Both circuits are activated by the multi-function switch(turn signal stalk) but separate contacts because the rear shares brake light bulb