LH-IG fuse keeps blowing

Hi guys! I have a 2015. Noticed yesterday morning that I didn't have any signal lights. Found a fuse under dash blown. Is is labeled lh-ig. 7. 5 amp. I replaced. Tried using the signal and it popped the fuse. Anyone ever have this problem? It must have been popped for a little bit because same fuse is for alternator and battery was about dead when I got home. Thinking maybe signal switch shorting? Hazards do work. So not a bulb problem. Thanks

 

First thing would be check the wiring going into the headlights/bulb sockets, something could have gotten pinched or loosened.

 

I’d have to look at the wiring diagram to see what all comes off that particular fuse - hazards working but not turn signals is odd.
Did you buy the truck new? Any aftermarket modifications that might have tapped that circuit?

 

I am second owner. No mods. I'm assuming that if the hazards work (all four signal lights working) then it shouldn't be a pinched wire under hood or back to tail lights. Does the signal lights and hazards use same relay? If so, the relay is working fine with the hazards. Wondering if signal switch in the column is shorting maybe?

 

Signal light wire got pinch, take out the lights and check. It takes a while to expose the wire.

 

Even though the hazards are working fine? You would think if it was a pinched wire, the hazards would pop a fuse too.

 

Also pull all 4 turn signal bulb sockets and look for rusted out contacts and corrosion. The sockets are replaceable. The passenger side of these trucks is known to get water in the sockets. I had issues with my 2013.

 

Wouldn't the hazards pop a fuse if there was a bad socket or bulb?

 

Not necessarily.....depends on the contacts and how they are wired. It's an easy check to rule it out though.

 

Agreed. Will try.

 

I have had it undercoated recently. Maybe some of it got into to wiring junction somewhere. That stuff creeps everywhere. Lol

 

Update: after popping a couple more fuses in the same spot (Lh-ig), I discovered that it is popping as soon as I turn the key on. Way before I try the signal lights. Pulled the bulbs too. I guess tomorrow I will start to eliminate things from that circuit and go from there.

 

Hazards and Turn Signals are all the same relay on the 2015 (PDF attached of the wiring diagram).

LH-IG is used in a LOT of circuits (depending on what your truck is equipped with). It is the "trigger" circuit for ignition on a bunch of different relays and components. With that fuse tripped, I would expect your radio to not work, your charging circuit to not work, and if you've got a column shifter - reverse lights, 4WD, cruise control, backup camera, BSM, parking sonar, Door Locks, and who knows what else.

 

Thanks man. As far as I can tell right now, when fuse is gone, signal lights don't work and charging. Radio works, back up lights work, and most other things in your list works. Weird. Thanks for your help!

 

Do you have a column shifter or floor shifter? Most of those other circuits power off a different fuse in floor shift models

 

Floor shifter.

 

Look what we found! Rubbing with a wire coming off of the brake fluid sensor. That was bare too.

 

that's the cause???

 

Yes. The yellow wire goes to the fuse and also goes to the alternator. It was next to the wire coming off of the break fluid sensor. Must have vibrated and rubbed with each other causing the casing to wear off and short with each other. Taped up and have not blown a fuse yet. Fingers crossed. Lol

 

Nice work…

 

Thanks. Some stressful sleuthing. Thanks everyone for the advise!

 

We ain’t that much help…lol
You did it all by yourself

 

I hope someone will find this useful someday. Next time you are under the hood, take a look there.

 

I have changed the title of the thread to match what was really going on.

 

Ok, this is the third time I’ve been left stranded because of this. The fuse does NOT blow, but I get no power to this one fuse, causing my NEW alternator not to charge, which means a quick loss of fuel pressure. I also have a new battery. Since I’ve got it, the battery light is on unless rpm’s are above 1500. Whether or not the battery light is on or not, I have 10.5-11 volts. Starts fine, just won’t last. Once again, the fuse is not blowing. I’m thinking it’s maybe the yellow wire previously mentioned in this thread. Then I have to find it. I NEED my truck very soon, but I can’t run it like this. HELP!

 

Its almost impossible to loose power to just one fuse in the interior fuse box. They are all tied together in a way. Do you still have power to the 20A 4WD, 7.5A ECU-Ig No.1 ???

 

^^^^This would be my guess as well.

 

Nice job!

 

I have power to the 20A 4wd, but for the like of me I can’t find the other lmao, I’ll try harder

 

Ok, so after I found it I felt like the biggest idiot ever, but I replaced both the 20A and the ecu-ig no 1 and I’m still having my issue, but yes I was getting power to them as well