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Old 11-10-2008, 02:06 PM
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Alternator to Fuse Block

Hello all...

I am looking at the possiblity of rewiring my vehicle or possible just putting in a simple fuse block. At this point I do not think I need to do an entire wiring harness. I will be running the usual....lights (through a separate aux relayed harness), heater, blinkers, dash lights, radio, HEI, wipers. I think that I will be ok running them through a hot ignition fuse block.??

I am running a 12SI alternator - coming off of the two tabs #1 is the excitor wire and that goes where???? Tab #2 I have going to the post and a 10 gauge wire from the post to the battery....then a wire from the battery to the circuit breaker before the fuse block.

Does this sound right? Am I close?


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Old 11-10-2008, 05:11 PM
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-- The exciter wire (#1) goes to a switched power source that is only on when the ignition is on.
-- The sense wire (#2) can be connected to the post on the alternator, or for more accurate charging performance it can be connected to a junction in the wiring harness.
-- The 12 volt battery connection should have a 8 gauge wire, if this a 94 amp 12si. For a 63 amp alternator the 10 gauge wire is okay. In either case there should be a fusible link at the battery end, two sizes smaller (numerically 4 higher) than the charge wire. For example, a 10 gauge wire should have a 14 gauge fusible link.

The connection to your fuse block should use a wire that is sized appropriately for the total amperage load. It should have a fusible link or fuse at the end that connects to the battery. This will provide the best protection against shorts.

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Old 11-10-2008, 05:28 PM

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Check out Painless or Ron Francis wiring, they make in-expensive fuse blocks and wiring harnesses that will make your day much easier.
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Old 11-10-2008, 08:29 PM
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I did buy a Painless fuse block that starts from the battery and goes to a circuit breaker then to the fuse block. It has a set of relays that connect to the ignition switch once in the on position flips power.

It sounds like I can just run the excitor wire back to the ignition switch. I would run it to the coil, but, I am running an HEI and I am unsure of where or how to hook it up.

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Old 11-11-2008, 07:02 AM
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Here is a wiring diagram. The field wire can be used to fire a relay for electric chole operation. The heavy B+ wire can go to the battery side of the starter relay, or a main power junction block, or to the main fuse block feed. The shorter the B+ wire the better.

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File Type: pdf Alternator.pdf (5.5 KB, 118 views)
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