Aux. fuse block

I want to run an Aux, fuse box to run the aftermarket stereo.

I don't want to molest the OEM fuse box as I want to keep the car in OEM spec as much as possible.

I've run new battery cables in 0 ga.

From the + side Terminal that I have a 4ga. wire, inline fused @ 60amp. That runs to a able Splitter Distribution Block. I've run an 8ga. wire to the amp.

I'd like to run a 2nd 8ga. wire to an Toggle Switch, then to a Fuse Box. I do not want the stereo run off the Acc. circuit.

QUESTION: Do I need to put an inline fuse ahead of the Toggle switch? If so how many amps? Maybe 20 amps?

Toggle switch tend to run from 5 -25 amp. ratings. What amp rating would you suggest?

The stereo head unit has a 10 amp. fuse. I believe power antennas are 10 amp. fuses. Those will most likey all that will be running off the aux, box for now.

Seems a little heavy overkill for just a radio and antenna? Instead of a switch you could run it though a relay and wire it to Ign so it powers off with the key, but most have a memory power wire that stay hot all time.
A fuse is always best to be as close to source (bat) as possible.

Yes, "over-kill" is my motto in anything I build. Never use a 2x4" if you can use a 2x6"



After taking a 2nd look at the circuit demands, I've rethought my plan.

I had over looked the need for a constant hot supply for the memory yellow wire to the stereo. So, on/off toggle 1st would not benefit me.

I believe I would be safe/correct in running 8ga. from the battery to supply the aux. fuse box. Then power through a 30amp fuse to the 50 amp toggle I found from an off-road/race supply to the power on the stereo head unit. The head unit has a 10 amp. fuse now.

The yellow constant will run through a 5 amp. fuse.

I believe I will be safe adding the powder antenna in the future as Eric suggest the 8 ga. supply should be able to safely supply 70 amps. I can not for see ever coming close to needing that level of power through the Aux. box.

The gauge of wire you decide to use will depend on length and voltage running through it. If you were to run the system in reverse, meaning your switch is on the ground side, you'll get your components to last longer and won't need as large of fuses cause you'll never get that really big spike.

endicott_jb said:

….If you were to run the system in reverse, meaning your switch is on the ground side, you'll get your components to last longer and won't need as large of fuses cause you'll never get that really big spike.

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Thanks. I 'll switch it on the ground side then.

Endicott - is that really true? Seems to me it will "spike" from zero to full current no matter where in the circuit the switch is located? (It's been a long time since I studied electricity)

Personally, I'd run the switch as close to the fuse block as possible. In a vibrating car, the shorter the length of hot wires the better.

From what I was taught when I went to UTI a few years ago, auto manufacturers have switched from negative load to positive load for that reason. It could be that they were blowin smoke up my @$$ but it seams legite. Especially since electricity flows backwards then what traditionally you would think. That is depending on how you learned electrical theory. Of course if you go by what an electrician friend of mine says, you just have to keep all the smoke in their tubes and boxes. Once you let the smoke out nothing works. I'll have to look through some of my books but I have a chart that says what gauge wires you need for how many feet and what size alternator you need to run all accessories.

I'm sure your right then. With everything solid state now, there may be a difference. My learnin thankfully stopped before I had to deal with transistors.

Look what I found. A bit more info then most need but cool nonetheless.




Hopefully UTI doesn't see this and try to sue me for sharing a page from their book.

IronRat said:

Thanks. I 'll switch it on the ground side then.

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If you (switch) the ground you will kill your memory too.

sneakysnake said:

If you (switch) the ground you will kill your memory too.

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D'oh!!! I kept thinking of just the power antenna. I forgot that you were putting your radio on the same circuit. Either way, you'll figure it out.