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201fireman

Alternator Wire Size

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I went to a 150 amp alternator on my SBC to BBC conversion.  The wire going to my alternator is a 10 gauge. Do I need to increase that and if so, where does it feed to?

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While it's unlikely you'll ever draw that much from the alternator to the battery, going to six gauge isn't a bad idea. 4 gauge even.

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A good friend of mine told me that the 10 gauge wire will work on anything up to 160 amp  but on this kind of a setup anything larger would not hurt.

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Thanks David.  Where does the wire go to?  I got a new wire harness a few years back during my build and they were all in a harness. My plan is to run a 6ga. from the alternator and tag it along the harness to wherever it is supposed to go so I don't have to rip into the harness.

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If you are going to use both wires, 10 ga is fine. That is what I did. I left my original harness intact, and added a 10 ga wire on top of it.

If I remember correct, the alternator output wire runs to the buss bar under the voltage regulator. (1971)

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Ok, so you added a 10 ga. wire to the existing 10 ga. wire so there are now two, 10 ga. wires? Not a bad idea.  I converted to an internally regulated alternator a few years ago so if my memory serves me correctly, I removed the regulator.

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Just for kicks, I'll show you guys what I did but it's far from stock.

The under hood fuse box has fuses for water pump, fuel pump, vacuum pump, two fans, headlights, AC, body, relays, 2 for EFI, and ignition coils. The AC system is modified to get all power from under the hood. The alternator is a 200 amp AD244 unit.

POWER.jpg

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I have 70 & 72 (not a 71) service manuals....the engine bay charging system wiring is slitely different between the two. Wire splice location(s) & component locations vary, but operate pretty much the same. I will say that the "common component" is the "hot-at-all-times" buss-bar (aka: junction block) at the Horn relay. Battery, charge circuits and  "high amp accessories" end up "connecting" to that point, if not directly, thru a splice. Also, running two smaller gauge wires from point "A" to point "B" is not recommended in the "electrical community"....

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I forgot to comment ....Paul Bell's modified wiring system (the diagram with the battery in the trunk) is very good!!!....maybe lacking a "max fuze" on the charge cable (I'll bet if he's a pro-audio guy, it is there, but just left off the diagram) 

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American Auto Wire is shipping their complete harness sets with a 6 ga. wire now, with a maxi-fuse block, to accommodate the higher amp alternators and loads. Another interesting book I read while researching the fuel injection addressed the charge wire/system as well. Sure, a 10 ga wire will work, but once you start adding loads like electric fans, fuel pumps, stereos, etc, the voltage drop will be a problem and could impact the ECM performance and cause drivability issues. 4 to 6 ga was that authors recommendation, keeping in mind it was geared more towards fuel injected, heavily loaded electrical systems.

Lightly or no mods could probably get away with less than that. The early AAW harness kits used an 8 Ga. wire and fusible links, but have now been superseded as mentioned with 6 ga .

 

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7 hours ago, 72Ragtop said:

running two smaller gauge wires from point "A" to point "B" is not recommended in the "electrical community"....

Oh, that darned electrical community. 

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Thanks for the info guys.  I am finding these:

https://www.painlessperformance.com/wc/30700

https://www.americanautowire.com/shop/6-gauge-alternator-connection-kit

The Painless kit says to run it to the battery. The American Autowire kit says to run it to the starter. Does it matter which? Also, I have a 10si alternator with the flat, two wire plug on it also. Am I ok to leave that the way it is? 

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10 hours ago, 72Ragtop said:

Also, running two smaller gauge wires from point "A" to point "B" is not recommended in the "electrical community"....

Actually, this is commonly done in the electrical field.

However, when paralleling conductors, they need to be the exact same length and terminate on both ends together. A 10 gauge wire handles 30 amps so two handle 60 and so on.

I would say it's NOT commonly done in cars as it's easy to replace one wire with a single heavier one.

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14 minutes ago, 201fireman said:

The Painless kit says to run it to the battery. The American Autowire kit says to run it to the starter. Does it matter which? Also, I have a 10si alternator with the flat, two wire plug on it also. Am I ok to leave that the way it is? 

If you have an auxiliary fuse box with added loads to the vehicle, the heavier wire needs to go there AND to the battery. Getting to the battery via the starter cable is just silly.

If you don't have an auxiliary fuse box or heavier loads than stock, just run it to the battery.

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http://www.madelectrical.com/electricaltech/remotevoltagesensing.shtml

Here is some good info on what to do with that flat 2-wire plug.

If you wade through all the technical info they have on their site, you will get a good idea of where improvement should be made, and what to leave alone.

Really there is a good wealth of info on the Mad Electrical site.

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I can attest to the great information on the Mad Electrical website.  I ended up buying most of the products that Mark offers on that site - the "new system", a few relay kits, HEI kit, the starter kit, the alternator kit, terminals, etc. etc...he should offer me stock for as much as I have bought from him over the years.  Anyway, I ended up completely redoing my underhood wiring with his products, and the difference is readily apparent.  No more weak spark, no dim lights, easy access (via the junction blocks) for wiring, and none of the previous issues exist any more.  I think what is the best part is the underhood junction blocks.  I ended up putting two under the hood - one over by the windshield wiper motor, and one out front by the original buss bar.  Unfortunately, Mark no longer sells those individually, but I did find a great source for them in boneyards - Chevy vans - or if you want a dual block, trucks have them.

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I guess I need to get up with Mark then... Thanks again guys for all of the help. Here I thought by adding a second accessory fuse block I was solving the issue lol. 

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