I keep blowing a turn signal fuse on my 03 f350, why???

the turn signal circuits are shorted,,the fuse blowing saved you from a fire.(burning harnesses)
faili on left or right or both and HAZARDS? SORRY 3 fuses to learn that.
USA answers, Chevy S10 only
there are 2turn fuses, I see, in the schematics.
LT-turn and RT-turn, so now you know which side is shorted. just a glance and bingo , side. bad know, cutting work in ;1/2.
but, there is 10amp turn fuse too, that runs the turn flasher module
so 4fuses, turn left and turn, main and haz main.
this is bad.

any thing in this whole turn system can blow fuse turn main, BLK.
but learning if only one side fails ,is great moment,
if both fails, the problem is this module or the turn swtich is shorted.

Disconnect all of the turn signals at the lens assembles. Plug in the fuse. If it still blows, you have a wiring problem and will need to trace the wires to find the grounded wire.If the fuse does not blow, then replace the assemblies one at a time until the bad one shows up. Also check your fuse box to see how much damage was done to it. Look for melted wires. Hopefully it did not do much damage.

Does the fuse blow on both left and right sides,or just blows randomly or as soon as you put the new fuse in?
Does it have tilt steering?I would check the wiring in the steering column to start.

does the right hand turn signal keep blowing the fuse. if so, remove one bulb (back) and see if it still happens. if not replace the bulb and remove the other bulb (front). if it still happens it sounds like something in the signal light wiring is shorted. best place to check for shorts and easiest is the connectors itself.

When a fuse keeps blowing everytime you replace it that means there is a short circuit along its cable. Check the flasher cables or call a car electrician to do it.

If you keep blowing the brake fuse than you have a short in the system. Unplug the brake switch. Install a new fuse. If it did not blow than the problem is after the brake switch. Next unplug the turn signal switch, then plug the stop light switch back in and press the brake pedal. Did the fuse blow. If not than the wiring is good in between the two switches. With the turn signal switch disconnected use a jumper wire in between the light green wire (power from the brake switch) and the orange with light blue wire (power to the right brake lamp). If the fuse blows than there is a short in the right side brake circuit between the plug in and the rear socket assembly. If the fuse does not blow than jump from the light green wire to the Light green with orange wire (power to the left brake lamp). If the fuse blows than the problem is in the left hand brake wiring circuit.

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You have a short. you will need patience to route the wires from the harness to the light source, and to inspect for frail damaged wires.

If there's one thing that gets my shorts in a bunch it's trying to track down a short circuit. I had a 79 Trans Am that did the exact same thing that you described. With out looking at it I would say that there is an exposed wire that causes short circuit. It may be in the turn signal switch, or even somewhere in the steering column.

sounds like you have a short in your turn signals
(tip 1) replace the fuse with a 20 amp breaker instead of a fuse if it is a intermitant short it should reset instead of going out completly
(tip 2) before you put the breaker in put a fuse back in and try to make note which direction you are trying to signal when it blows this may help you isolate the short it will at least tell you the side of the car the problem is at unless it is under the dash if it turns out to be in wires to sockets which is common problem area .chances are great all you will have to do is check light sockets and wires to them on that side of car front and back.good luck and i hope this helps
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feel free to contact me via email if you are unable to locate short.

one of the bulb holders is no good or wires trapped somewhere that feed indicator lights