My turn signal fuse keeps blowing why?

Our professional automotive electronics technician Jeff, provides the answer to a dead short.

Jeff Armer Jan 01, 2024

STOP/ TRN fuse #12 20amp, location - in the instrument panel fuse box. Is this the one? Fuse blows because you have a short circuit on the wiring that fuse protects. Do you know what that is?

Turn Signal Lamps
The STOP/TURN fuse in the instrument panel (I/P) fuse block supplies battery positive voltage to the body control module (BCM) for the turn signal lamps. When the turn switch is placed in the left or right position, ground is applied to the BCM on the left or right turn signal switch signal circuit. The BCM then applies voltage to the appropriate front and rear supply voltage circuits.

Grounds for the various lamps are as follows:

• G100 supplies the right front lamps

• G101 supplies the left front lamps

• G400 supplies the right rear lamps

• G401 supplies the left rear lamps

https://www.youtube.com/watch?v=oKCLzf4va7M&t=807s

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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.

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.

you have a short in one of the light sockets or a worn wire from the wiring harness. could be the flasher assembly. are the turn signals different bulbs from the brake lights? Does using the brakes blow the fuse? (Rear lights or brake light switch on brake pedal). left or right turn signal blowing the fuse will tell which side has the short. 4 ways only, replace the relay.

first thing i guess to understand what is going on here ,is a little back to basics on how turnsignals work , first item you have is power fuse then it's off to flasher module than it goes to the turnsignal switch on colum ,of course anywhere on it way to there the power could got to ground and cause the fuse to trip, now the power depending on Left or right selection , is directed to lights on both front and back of truck,thankfully rangers don't have em on the side) now any place in this pathway the wire could go to ground and blow the fuse, now to troubleshoot and narrow down the area that fault is located , (1) replace fuse with correct size and ck for proper fit in fusebox and start and operate truck for a few minutes DO not use turnsignals, ck fuse is it still good if so go to step 2 if not stop and ck wire conditions in steering colum and switch(2) start truck and try right hand turn signal only verify lights working ,Ok yes/no if not replace fuse and try left side same way, Ok yes /no if right or left side only blows fuses take ALL bulbS OUT of lights and try again , if fuse still blows then look for wire fault on that side of truck if fuse is still good then look carefull at light bulb sockets for rust and powered corrosion (ill bet an 87 has some ) you may need to replace bulb sockets , they do sell em in autoparts stores .

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.

COULD BE BLOW FUSE.FAULTY TURN SIGNAL SWITCH OR FAULTY TURN SIGNAL FLASHERS WHICH IS LOCATED FUSE / RELAY BOX JUST LEFT OF THE STEERING COLUMN.

The flasher unit will not cause an overload in the circuit.Activate the four way flasher and if the fuse does not trip then it appears there is a short in either the left or right signal circuit when the steering wheel is turned.The position of the steering wheel will determine which side is shorting out if this is the cause

Check the front and rear (although probably the rear) turn signal bulb socket for corrosion and/or water intrusion. If you find corrosion attempt to clean (but you will probably have to replace the socket and bulb). For water intrusion you will probably have to replace the break lamp assembly.

left side u got a short
u can wire up a buzzer or light to plug into where the fuse goes that blows when u turn on ur left blinker the buzzer will sound or the light will come on ,while the buzzer is on take apart left signals
and check wiring by moving harness around ,when u find the short the buzzer will quit