Death Of An Alternator

[stalephotograph 10+ year member]

well i just ordered a new 200amp alt from dbelectrical out of tennessee for $224 shipped. my stock alt which is like 105amps started dieing on me last summer. yesterday i had my stereo going and all of a sudden everything just shut off then came back on. this morning on my way to work, i had my stereo on again as usual and every light possible in the gauge cluster came on. i noticed in the past few days my airbag sensor light would come on and off when the stereo is up.

i knew it was only a matter of time for it to go out. i figured id solve the problem before im really in a hole. not to mention when i install my bag setup i will be running a 12v compressor pulling around 70amps everytime its on for at least 3minutes at a time.

my question for the big stereo gurus, is this. i plan on upgrading the "big 3" under the hood....positive battery post to alternator post, negative battery post to frame and engine ground to frame. when i upgrade the pos batt post to alt what size fuse should i run in between?? thats my main concern. i will be running hopefully 0gauge for all of this.

so far ive been told, 100-150amp fuse, 250 amp fuse, and not to fuse it at all. ive never gotten a clear answer for this. im driving a 98 s10 that came stock w/ a 105amp alt.

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[Famous_78]

Evertime ive seen it done theres wasnt a fuse idk why you would fuse it anyway.

 

[bryce-man 10+ year member]

you would fuse it to protect the wires and not burn em.. but i dont htink you could pull enough to burn em

also if you get in a crash and it gets cut, the pos gets grounded .. sending out crap loads of sparks the fuse kills that curcuit right when it happends so no sparks

...

but even knowing all that.. i dont fuse mine

.. 2 runs of 1/0

 

[Famous_78]

thanks it all makes sense now.

 

[Omarvelous 10+ year member]

If you want to fuse however, 300-350 is good enough, being that it's a short run of 0 wiring. Like said, protecting the wire.

also if you get in a crash and it gets cut, the pos gets grounded .. sending out crap loads of sparks the fuse kills that curcuit right when it happends so no sparks

That could still happen fuse or not.... That's what good wiring and crimping will TRY to prevent.

For example, the wire from batt to fuse could still ground....

 

[helotaxi 5,000+ posts]

If you get in a wreck bad enough to cut the underhood wiring, typically the battery grounds out to the hood and no fuse in the world will prevent that. Rolled a car 3x without blowing a fuse or shorting a battery. If it's all securely mounted and wires are smartly routed, a fuse between the battery and alt isn't needed. There isn't one from the factory.

 

[soydeedo 10+ year member]

my stock alt to batt runs from the alt to the fuse box, is fused with an 80a fuse [crappy 70a stock alt], and then goes back out to the battery.

you're right that in all likelihood wire damage under the hood isn't going to happen, but it's a safeguard just like everything else. and also a lot of people have distribution blocks with nonconducting caps on their positive terminals so your comment about shorting out the battery with the hood isn't always true.

shrug

 

[Sunfire01 10+ year member]

Keep us updated on the new alt from db electrical. I want to order one from there eventually for my car.

 

[stalephotograph 10+ year member]

well i talked to a guy i know that works at a car stereo shop as an installer and here is what he had to tell me.....

wassup man???? good to know you're thinking like this; a lot of people just try to add batteries instead of beefing up their alternators. as far as your question is concerned, look first to see if your truck is fused between the battery and the alternator. my toyota isn't fused, but the GMC has a 150 amp fuse in it at the alternator. if you want to really get technical about it, you can sum up all of the fuses in the truck (or you can look for a really big primary fuse in your underhood fusebox; it usually is located close to where the positive battery wire (4 guage) runs into the fusebox). that will tell you how much current your truck's electrical system is designed to handle. then add together the total current draw you are adding (i.e. the bag setup and the stereo). that will give you how much current your alternator has to handle. since nobody connects anything to the alternator, the battery will be supporting the same amount of current by acting as a "buffer" between the alternator and all of the electrical equipment. once you know how much "total" current the truck will have to support, i would add 20 to 30% to that value, cuz as your voltage drops from 14.4 with the engine running (and it will, if you have a pretty good stereo), the current draw will slightly increase. if i were you, i would put a 200 amp circuit breaker inline between the alternator and the battery; that way, if it pops, you aren't stuck on a dark highway unable to charge your battery. you can simply turn off the stereo, turn off your heater or a/c, and reset the breaker.there.....easy as 1,3,2.......Mr. Green

call me if you wanna bring it by...i have 200 amp circuit breakers in stock.....

i will definetly let you know about the dbelec alt.

 

[UndercoverPunk 5,000+ posts]

If you did a good job running the wire you would probably get away w/o a fuse....

It is however good practice to fuse all power wires. In which case you should fuse for the wire.... which with 1/0 would be any value between the amperage of the alt and the max load the wire can handle.

So a 200, 250, or 300 amp should do.

 

[Chevyaudio 5,000+ posts]

Sounds like he is trying to sell you a circuit breaker.

If you want to fuse it. Fuse it with a 250 amp fuse. Counting up the fuses is pointless...because you are fusing the wire to protect the wire not the truck electrical...The fuses in the fuse box are designed to protect the electrical system of the truck.

 

[helotaxi 5,000+ posts]

my stock alt to batt runs from the alt to the fuse box, is fused with an 80a fuse [crappy 70a stock alt], and then goes back out to the battery.

And mine ran from the battery + to the starter and then on the alt, with no fuse anywhere (165A factory alt). Not all are fused from the factory.

you're right that in all likelihood wire damage under the hood isn't going to happen, but it's a safeguard just like everything else. and also a lot of people have distribution blocks with nonconducting caps on their positive terminals so your comment about shorting out the battery with the hood isn't always true

If you think that those battery terminal covers will withstand any kind of impact and protect from anything in a crash, you're sadly mistaken. They are there simply to protect from accidental contact under normal circumstances. In a crash, all bets are off. Still very unlikely that the underhood wiring is going to get shorted, though. I can tell you that I didn't bother with a fuse when I did the 'big 3'.

 

[Chevyaudio 5,000+ posts]

I didnt fuse my big 3 either...

But then again I am very cautious when I route my wires. Looming and protecting them from heat and abrasion at all costs.

 

[stalephotograph 10+ year member]

hm sounds like i may be fine w/ out fusing the wire. i just wasnt sure if i should chance of burning up the wire somehow.

 

[SSon22s 10+ year member]

Im interested to see how it works, I have been looking at motorcityreman and dbelectrical...