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Old 11-06-2019, 04:18 PM
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convert 56 chev. to alternator

Hey you all I am changing my generator out and going with an alternator.
I have heard someone ask if I want a one wire conversion or a two wire?
I would like to keep my idiot lights, so which way and where is the best to
purchase. Thanks . Duane

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Old 11-06-2019, 04:33 PM
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Do NOT get a one wire. There's a reason why GM never installed them in cars from the factory. And the "two wire" is really three. Two in the plug and one heavy wire to the threaded BATT stud.
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Old 11-06-2019, 05:11 PM
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Thanks for reply. This may be a dumb question, but do you know what is the reason for a 2 or 3 wire conversion as apposed to a one? Duane
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Old 11-06-2019, 05:28 PM
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Quote:
Originally Posted by db flyer View Post
Thanks for reply. This may be a dumb question, but do you know what is the reason for a 2 or 3 wire conversion as apposed to a one? Duane
The main wire from the BATT post on the alternator to the junction block is the primary charging wire. The two wire plug on the factory alternators includes a SENSE wire and the FIELD wire that operates the idiot light. The SENSE wire also runs to the junction block and senses voltage there (as opposed to at the alternator) to automatically adjust the voltage regulator output to account for any voltage drop in the wiring. The FIELD wire actually serves two purposes. In addition to operating the idiot light, it also serves to turn on the voltage regulator at low RPMs to ensure the alternator is charging even at idle. Keep in mind that GM cuts every penny possible in building their cars, yet they kept these extra copper wires instead of using a one-wire design. Common sense should tell you that they did this for a reason.

In your case, two of these three wires already exist in the original harness. The heavy charging wire from the generator to the junction block bolts directly to the threaded BATT stud on the new alternator. The brown idiot light wire already runs to the old voltage regulator. Simply connect it instead to the FIELD terminal in the alternator plug. Now run a new wire from the other terminal in the plug to the junction block and you're done. This assumes you are using a 12SI style alternator.

You may want to consider a CS130 instead. I like to use the CS130 from a 1989-1990 Oldsmobile Custom Cruiser with 307 motor. It has 105 amp output, bolts to any 1960s GM alternator bracket, and comes with a V-belt pulley instead of a serpentine pulley. This ACDELCO 3351011 CS130 brand new is under $70 at RockAuto right now. The CS130 uses a four wire plug in addition to the threaded BATT terminal. In that case, simply connect the SENSE wire to the "S" terminal in the plug and the FIELD wire to the "L" terminal (for "light"). Ignore the other two terminals. I've had one of these in my 1962 Olds for nearly ten years now.

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Old 11-07-2019, 06:14 AM
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I would discard the old heavy charging wire and use a AWG8 or AWG6 wire from the Alternator to the Starter motor Battery terminal depending on the alternator output. As the old heavy cable most likely not be able to cope with the increase in amps.

Last edited by brading; 11-07-2019 at 06:40 AM.
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Old 11-07-2019, 09:08 AM
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Quote:
Originally Posted by joe_padavano View Post
The main wire from the BATT post on the alternator to the junction block is the primary charging wire. The two wire plug on the factory alternators includes a SENSE wire and the FIELD wire that operates the idiot light. The SENSE wire also runs to the junction block and senses voltage there (as opposed to at the alternator) to automatically adjust the voltage regulator output to account for any voltage drop in the wiring. The FIELD wire actually serves two purposes. In addition to operating the idiot light, it also serves to turn on the voltage regulator at low RPMs to ensure the alternator is charging even at idle. Keep in mind that GM cuts every penny possible in building their cars, yet they kept these extra copper wires instead of using a one-wire design. Common sense should tell you that they did this for a reason.

In your case, two of these three wires already exist in the original harness. The heavy charging wire from the generator to the junction block bolts directly to the threaded BATT stud on the new alternator. The brown idiot light wire already runs to the old voltage regulator. Simply connect it instead to the FIELD terminal in the alternator plug. Now run a new wire from the other terminal in the plug to the junction block and you're done. This assumes you are using a 12SI style alternator.

You may want to consider a CS130 instead. I like to use the CS130 from a 1989-1990 Oldsmobile Custom Cruiser with 307 motor. It has 105 amp output, bolts to any 1960s GM alternator bracket, and comes with a V-belt pulley instead of a serpentine pulley. This ACDELCO 3351011 CS130 brand new is under $70 at RockAuto right now. The CS130 uses a four wire plug in addition to the threaded BATT terminal. In that case, simply connect the SENSE wire to the "S" terminal in the plug and the FIELD wire to the "L" terminal (for "light"). Ignore the other two terminals. I've had one of these in my 1962 Olds for nearly ten years now.

Thanks for the good info. I will print this out and go shopping. I doubt that I could find a used mounting bracket, but will research to see if some used bracket it the salvage yards may work.
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Old 11-07-2019, 12:18 PM
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What does your generator bracket look like. A picture would be good.
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Old 11-07-2019, 08:36 PM
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X2 on the ditch the old charge wire.



#1 it is not heavy enough.


#2 on a 56 anything, unless that car has been stored in a vacuum, the cotton braid covered rubber insulation is a fire hazard. I would bet that anywhere you move a wire, the insulation will shatter. 50+ years of exposure to the environment would have turned it to carbon.


I have seen mounting brackets cobbled up, do yourself a favor and find some brackets from a 70's era chevy pickup, these will fit the engine and the alternator and save time. They also will secure it properly, for easy belt adjustment and tension stability.


On anything that old I would seriously look at a complete rewire job.
Painless harnesses are a good way to go.


I never trusted Idiot lights for anything, Install a voltmeter not an ammeter.
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