Half of my fuse box is shorted out, drawing massive current.

[MisterWolfe]

96 gmc c3500 6.5td 4l80 2wd, half of both fuse boxes light up, i marked all the fuses that short out, i truthfully dont know if the relays are supposed to light up, but they do, I dont have a diode 1 jumper, or the air relay, but thats a gas thing im pretty sure, taking individual fuses out makes no difference anywhere, all shorts draw equally 4ish amps, my ac blower motor cuts off on max, my oil pressure light freaks out every once in awhile, and im pretty sure my tc doesnt lock in od, im driving 65 down the interstate, and my truck is all the way at 2600rpms, im pretty sure its not right, but I don't know.

 

[MisterWolfe]

Maybe I'm missing a ground, if I am its not there, I have checked all the ones that i have.

 

[sewlow]

Sounds like a dead short.
These trucks do funky strange things, seemingly unrelated, with poor contacts &/or ground wires.
Check the rear lighting & trailer hitch harness for bare/broken wires. Common problem.
Original ground wires? 25 years old. That green corrosion you might of cleaned off at the attachment points more than likely has crept considerably further back into the ends. It could probably be through the whole length of the cables by this time.
Do 'The Big 3'.
5vortec7 sells a proper kit with the right lengths for these trucks.
Manufacturers only wire vehicles to the basic minimum standard for the accessories they're originally equipped with. Start adding stuff, lighting, winches, stereos etc. & that factory shortcoming becomes apparent. Add in some old questionable cables & seemingly unrelated quirks start to occur.
Doing The Big 3 will alleviate that, making your electrical system much more efficient, even without any additional loads.

 

[thegawd]

now I'm sorry if this is a dumb question but, what do you mean by...?

half of both fuse boxes light up

did all of those fuses blow or are you simply reading voltage or are you using a test light thats lighting up?

all of the fuses are 12V+ and half of them are always hot. the other half come on with the ignition.

I'm just thinking and making sure were all understanding what's going on there.

 

[mattillac]

Welcome to the forum.

Have to wonder about the AUX A & AUX B fuses there (if they are marked and lighting up as you say/drawing 4 amps), I would figure those just feed the AUX A & B post at the top of the fuse box? If that is the case, you could probably (temporarily) remove whatever is attached there and retest, make sure you meter / testing method is correct and / or fuse box is good / bad.

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Would figure that is the easiest place to start, I imagine that those two circuits, after leaving the fuses are a very limited distance(from the aux fuses to the aux threaded screw posts).

 

[MisterWolfe]

Welcome to the forum.

Have to wonder about the AUX A & AUX B fuses there (if they are marked and lighting up as you say/drawing 4 amps), I would figure those just feed the AUX A & B post at the top of the fuse box? If that is the case, you could probably (temporarily) remove whatever is attached there and retest, make sure you meter / testing method is correct and / or fuse box is good / bad.

You must be registered for see images attach

Would figure that is the easiest place to start, I imagine that those two circuits, after leaving the fuses are a very limited distance(from the aux fuses to the aux threaded screw posts).

Nothing is hooked to aux b, aux a however is the aftermarket trailer brake power, ive already traced all the wiring for that, its not shorting on anything. And the aux circuits are connected to 2 studs on the same fuse box in the same place relative to the picture, they're just 2 hot posts. And every fuse that is lit up, on 2 freshly charged bats pulls between 4.16 amps and 4.19, all the time, all at the same time, and the amperage goes up as I pull fuses out, the fewer fuses the higher amperage. Taking all fuses but any one fuse out and Im pulling around 18-20 amps off whatever circuit I leave connected.