How to change mirror turn signal light, 2009 f250

You might possibly have a bad flasher module.

Have you check the light bulbs

I have changed many of these...Everytime I inspect one it is always the light that is faulty...and that is all different makes..I have found some have a left and right fuse but it was always the light..The mirror will slightly pivot..carefully pivot mirror slightly inward you will notice it is only held on with plastic clips..Use a good flashlight.....you can actually see behind mirror better at night with a direct beam small led pocket light...use a pocket screwdriver and carefully pry the clips away from mirror while softly pulling on mirror...All you have to do is release the 2 upper and lower outside clips and it will slide out..Then you will see the 2 screws that mount the signal light to the mirror housing..just remove and replace..re-install all the way it was removed...Do it carefully....easy job...

Well the brake light and turn signal circuits are on two different fuses, but they both go thru the turn signal switch.
So I would start by checking for power in and out of the turn signal switch for each circuit.

is this a plow truck? Either way i would start with the switch. Try doing simple continuity tests on the switch. if power doesnt flow when the switch is pushed in a direction, then replace the switch. If its not that i would try jumping wires on the mirror it self to test it. You have to know which wire is ground coming from the mirror.

- Adjust the mirror so the mirror glass is in as far as it will go (meaning if you were looking in the mirror you would see the side of the truck)

- Look inside the mirror housing
- Locate silver clip
- Using a flat screw driver, push the clip in
- Lenses will pop out on the outside
- Remove bulb
- Replace bulb
- Snap back together when new bulb in place.

not bulb led light part of mirror dealer, some auto stores or online parts

You could visit the dealer for that. Usually they print it out for free.

Im Not Sure About The Disasembling Part But The Led Lights Are A Single Unit To Fix The Bulbs That Are Out you Will Have To Change The Whole Light Assembly in Most Cases

Have you checked the fuse yet?