fuse blew, why?

[M@nJo 10+ year member]

i was attempting the big-3 upgrade and my positive batt to postitive alt didnt work out well. the anl fuse i used (100amps) blew and caused my battery fuse in the fuse box to blow as well with it. heres some basic info:

-my stereo amp is a 40amp fuse and it is 500rms

-i used 4awg power wire to amp from batt

-my big-3 wires are also 4awg

-i used an ANL type fuse which was rated 100amps

as soon as it happened, i was stuck with the car not starting as the battery fuse was blown. so i ran down to a local kragen and bought a replacement for the fusebox fuse for the battery. which was a 80amp rated fuse (its those cube style kinds with 2 ends that have holes for bolts to hold them down)

so my stereo amp uses a 40amp fuse, my battery fuse from the fuse box is a 80amp, and im using 4awg everywhere... should i try downgrading to a 80amp ANL fuse instead of 100? or should i be going higher?

(another '?': would doing the neg to chassis AND engine to chassis help my electrical system alone without the alt to batt?... any benefit?)

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[jacko 10+ year member]

use 150amps,(not anything higher on 4gauge) i wouldn't be suprised if a 100amp fuse blew from alternator to battery, an alternator can put out more power than 100amps sometimes, depends on the car, also, did you replace the old wire from alternator to battery(thats a no-no, only add wire).

 

[M@nJo 10+ year member]

i didnt replace any wire, i add onto it for all he big-3 wires.

are you sure about the 150amps? i thought if a fuse blows, its best to go lower than higher?

i read it here: http://www.bcae1.com/ under "fuses"

would i be safer with 80amp or 60amp?

 

[johnecon2001 5,000+ posts]

You might have a short somewhere. I would check all the new wiring before you do a new fuse.

And if the fuse is blowing because it can't handle the amount of current that the system needs. but the wire CAN handle MORE current.. then the correct move is to purchase a larger fuse.

 

[M@nJo 10+ year member]

i forgot to mention that my factory alternator is 70amps and im using the factory battery as well if that matters.

i think the 4awg wire im using for the alt to battery be too large since im only pushing 500rms watts off my amp that uses a 40 fuse. would it be a good idea to invest into some feet of 8awg wire for my last step of big-3 ? then fuse it with an 80amp or so.

 

[johnecon2001 5,000+ posts]

8 awg is a waste of time. You dont seem to be getting the point that bigger is better here. The bigger your wire the better the flow of electrons.

 

[M@nJo 10+ year member]

it makes sense that a larger fuse is the way to go BUT after reading thru that one site where it says its best to go to a lower rated fuse if it blows..

=/

 

[squeak9798 5,000+ posts]

it makes sense that a larger fuse is the way to go BUT after reading thru that one site where it says its best to go to a lower rated fuse if it blows..
=/

You are misunderstanding what he is trying to say on that site //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

On that site, he was saying that if a fuse blows for no apparent reason at all (i.e. after years of use it just blows one day), to temporarily replace it with a smaller fuse size, because there is a high likelyhood that something inside the amp or another component is damaged (and is what caused the fuse to blow). After you replace the fuse, he goes through a few quick "troubleshooting" steps to aid you in checking if a damaged component was the reason for the fuse blowing.

What we are saying is that if you simply didn't use a big enough fuse, and regular high current flow is the reason that the fuse blew, then you simply didn't use a large enough fuse and need to move up a few sizes.

Two totally, totally different things //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

 

[M@nJo 10+ year member]

oh snap. didnt know that. thanks for the input there. i was reading as if it applys to any fuse in general.

hmm, 125 amps or 150amps fuse?

amp = use 40amp fuse/500rms

factory alt = 70amps

4 guage everywhere

i heard your suppose to run the size fuse as large as your stereo amps?

and lastly, whats the recommend amp size for 4awg?

 

[M@nJo 10+ year member]

hey, can anyone let me know whether i should go 125amp or 150amp fuse in my situation?

need to complete my DIY =D

 

[EvOLuTNMotORs 10+ year member]

what i would do FIRST is basic electrical troubleshooting. LOOK FOR A DAMAGED COMPONENT OR A SHORT IN THE SYSTEM !!!!!! blowing a fuse usually means these are one of the factors. check all of your connections, i have had people come to me with home jobs and had connectors close enough to cause arcing, prompting fuses to blow. just keep things like this is mind when troubleshooting. if there is a serious problem and all you do is upgrade fuses you will do more harm than good, because you are now letting the fault continue for a longer period of time. this can cause excessive electrical and component damage (failure) fires etc....remember your components are are designed and protected by rated fuses for a purpose (protection) of the circuit. i think you should troubleshoot more and isolate the problem and correct it (not upgrade fuses).

1 look for pinched wires

2 burn marks caused by arcing

3 exposed wires

4 strength of connections made (no loose splices, etc...)

it's time consuming but very effective

 

[M@nJo 10+ year member]

^thanks for the tips there. but i have hard time understanding 1-3.

also, i think my ring terminal might have touched the alternator housing cause i tightned pretty hard with the "pop-out side" of the ring terminal facing against the alternator housing (doh).

as for fuse, im thinking about going with 60amp because my alt is only 70amps. im thinking the other 10 amps will go thruout the stock wires. what you guys think?

 

[EvOLuTNMotORs 10+ year member]

1 means maybe somewhere in your wire routes you could have pinch a wire with anything in the way (car seat, under dashboard) causing a short.

2 as you said the wire touching your alt housing you would see burn marks signaling that electricity passed through that housing

3 goes back to 1 meaning you have a cut in the insulation exposing the wire inside (causing a short)

as for the fuse go with whatever your equipment had to begin with. that is your best bet to be on the safe side

 

[M@nJo 10+ year member]

its all additional wiring, no replacements. =/