I have a different situation from most...I put my battery up front, but I did not like the idea of a energized giant welding cable running under the car next to the gas tank; So I installed a Ford style separate starter solenoid up front so the big wire is only energized when I am stating the car....Then I ran another, smaller wire to actually power the car....It all works like a charm (Hey something I did worked!) but I want to install either a fusible link or an actual fuse on that smaller power wire so that, in the event of getting hi-centered during an accident, it shorts and dies...instead of it shorting and >ME< dying!

Having some trouble getting the info locked down....This would be power from the battery to run everything.....Basically connects the battery to the battery junction box back in the right side of the engine compartment. What size fuse- or what gauge fusible link should I have? Would a 30A fuse work? (Seems like it should be bigger!) Oh yeah, although I do not have power windows/locks/mirrors nor A/C, I may add A/C later if I move to Redding, CA....(hot, hot, HOT!!)

Fusible links at The Cave
http://web.archive.org/web/...ocave/ecmwire_fl.htm

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What happens to a wire carrying excess current is that it gets hot, and if it gets too hot, fire may ensue.

The bigger the wire, the more current it can carry before melting.

The role of a fuse is to protect the wire downstream of it from potentially damaging currents.

Therefore, the fuse you install depends on the wire gauge you select.

The thicker the gauge, the bigger the fuse you can put (while still adequately protecting the wire), and the more current you can draw without blowing said fuse.

If the wire is too small, then (to protect the wire), you are required to install a low-current fuse, and then you may end up blowing fuses all the time with normal use.

The following document shows maximum allowable currents (see last page) for different types of wires and ambient temperatures:
http://www.littelfuse.com/~...elfuse_fuseology.pdf

Ok.......How much current does the system draw at maximum....Say, headlights on and heater fan at full blast? 30 amps? 60 amps? Or more? I am using a AWG 8 wire to connect the battery to the battery block...Approx' 15 feet long.....I just want it to die if it shorts out and NOT short out if I turn the fan to full blast while driving at night......

It doesn't matter what the system draws... since you've picked a wire gauge already (8 AWG), then depending on the wire type and ambient temperature, your maximum fuse size is set.

If you get nuisance fuse blowing with what you have, then that means the wire/fuse combo was too small.

[This message has been edited by pmbrunelle (edited 12-14-2017).]

quote Originally posted by pmbrunelle: It doesn't matter what the system draws... since you've picked a wire gauge already (8 AWG), then depending on the wire type and ambient temperature, your maximum fuse size is set. If you get nuisance fuse blowing with what you have, then that means the wire/fuse combo was too small.

To Complete that thought....

Fuseable links are aways two gage sizes less than the base wire. IE it its 16 use 18 etc.

Knowing the size of the base wire is the trick. So in your case....it's AWG 10

quote Originally posted by Gall757: Fuseable links are aways two gage sizes less than the base wire. IE it its 16 use 18 etc. Knowing the size of the base wire is the trick. So in your case....it's AWG 10

Wire is available in increments of 2 AWG, so two sizes smaller means a 12 AWG fusible link for an 8 AWG wire.

I don't think a 10 AWG wire would burn quickly enough to protect an 8 AWG wire.

[This message has been edited by pmbrunelle (edited 12-14-2017).]

quote Originally posted by pmbrunelle: Wire is available in increments of 2 AWG, so two sizes smaller means a 12 AWG fusible link for an 8 AWG wire.

^ This is correct.

FL to do this is installed next to battery and then wire to "box" under C500.
Data FL to protect wire used are easy to get but get data from Little Fuse etc not from Ebay vendors.
Most stores carry only 1-3 size FL but http://www.whiteproducts.co...ible_link_wire.shtml carries most sizes from Delphi that started as spin-out of GM part divisions.

Can use bigger wire and link because will be longer then OE between the two locations but 10 feet isn't a huge change. Wire vs Amps charts are 100 or 1000 feet.
If adding high powered sound lights etc then even in factory setups need many changes and simple one wire from battery to rear is often not enough here.

Example: See my Cave, Headlights If your relays run to new battery box then may need heavier wire battery to rear so alt can handle battery charging and hot light bulb but often only 1 or 2 size bigger. If OE wire is "12awg" then new wire could be "10awg." (ALL GM cars after late 70's have Metric Wire Size. See my Cave, Wire Service )

Battery Does Not see AC and others draws even when engine on. If it does then likely have Alt problems.
HL bulbs and may HL PW PL "motors" are only big draw w/ engine off normally. HL bulbs draws a lot, park/tail not so much and have park only won't drain the battery fast. All of those motors should only run for a few sec to run them open/closed.
See my Cave, Watt Story

If worried about "Crash safety..." Be aware FL & stater relay are nice ideas but most front mount batteries in Fiero can short out in a crash even w/ these. Group 75 and related are ~32# and can break loose easy in a minor crash. Having lived is a rust state w/ high road salt use I've seen many rusty OEM mounts and rusty or just poorly installed Aftermarket mounts fails even just driving on crap roads. Worse for FM Fiero battery w/ glass/metal try/box just mounted is plastic spare tire wall. Loose Battery side or top terminals can short to spare tire, metal try/box, radiator fan for a start. Short across battery can dump 300+ amps.
Even when battery 100% stays put... rad fan etc can be pushed/fall on to battery cables/terminals.

Is why many OE batteries have + term covers so tools, cans, etc won't short and cause major problems. Example: Most pressurize Cans can explode. Product can be water based but uses propane et al as propellant and shorted dumps 300+ amps burns thru the cans and ignite this. But these covers often won't help when in a wreck.

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Ogre- That is why I went with AWG 8- distance vs load + Alt charging battery. I am lucky that I live in CA where we rarely have any bad rust.....I also have the spare strapped down over the battery........I'm not so worried about the battery shorting up front and possibly starting a fire.....I am more worried about a simple high-centering and the powered wire shorting against ground/fuel tank and then.....(Colonel Blake quote)..."Booooommmmm" (Hopefully I won't have a toilet seat around my neck!)

Would a 30 amp fuse in a holder do the trick? If the wire shorts, I just want it to immediately.....die.....But, obviously, I don't want the power to die every time I turn on the heater fan, or, after a hard start, die because of alternator load to the battery......

Should never Fuse to replace a FL.
30 amp can blow easy for many reasons. Most holders, weather poof or not, aren't rated to handle 30a or 8g wire. Big Fuse often won't blow before crap holders melt or causes a fire.

Max Fuses w/ higher values may work but finding a weather proof case to use in a car can be hard.

(Colonel Blake quote)..."Booooommmmm"...
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