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1947 Chevy coupe

Guest Lasermangene

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Guest Lasermangene

I want to change from a generator to a alternator in my 47 chevy it already has been changed to 12 volt and I would like to install alternator and haven't been able to find any thing on how you go about doing it, is there any place I can find what I need to do? Never done it before so not sure what all has to be done. It has a 235 6 from 55 chevy truck for a engine. The part I'm stuck on is how to hook up the DA plug and what to do with the voltage regulator if anything and how it all hooks up.

Edited by Lasermangene (see edit history)
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How modern of an alternator? A GM 10SI is a popular one. Plenty and cheap (great oxymoron).

Some points to consider:

Pick up a spare generator bracket to modify, hack, etc.

Pulley / belt mating issues.

Reworking the wiring harness. I assume the current external regulator is a fair distance away from the generator?

I am sure others will chime in soon.... got to run.


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I found this on THE OLD ENGINE site some time ago so I hope it is OK to post it here as it seems to be a fairly good explanation. They do have a full page on 6 to 12 volt conversion how to's if you want to look it up.

10SI Alternator Wiring

The 10SI has three terminals (including those with a 1 wire regulator).

The large "BATT" terminal which gets connected to your battery positive. (Or Terminal Post if your vehicle is so equipped).

And a dual terminal connector. (Repair pig-tails for this connector available at any autoparts store. Or, salvage with alternator if pulling the alternator from a vehicle).

The #1 Terminal. (Marked with a "1" on the case)

This terminal is used to connect to the dash warning light.

For the warning light, a lamp is wired in series with a switched voltage source. During normal operation the lamp stays off. If the regulator is damaged, the #1 terminal provides ground, and the warning lamp will light. Usually.

This terminal is also active on 1 wire regulator equipped 10SI alternators.

The #2 Terminal. (Marked with a "2" on the case)

This terminal is used to excite the 10SI into operation. (3-wire 10SI)

It is connected to the battery positive.

For simplicity you can connect the #2 connector pigtail directly to the "batt" terminal on the alternator.

The terminal is present on 1 wire regulators. Used only for those that require the stock connector to fit snugly.

If you are converting from a 3wire 10SI to a 1 wire regulator you can hook up all your stock connectors, and run it as is. However, thats wasted money unless you plan on cleaning out some wiring under your hood.

If the 1 wire is for cleaning out wires, you only need to retain the "BAT" wire. The #1 & #2 terminal wires can be eliminated. Don't be surprised to find that the #2 wire only goes a short way into the harness and spliced into the "BAT" wire.

The 1 wire regulator comes with a dust plug for the #1 & #2 terminals.


Some other tidbits available from AC Delco for wiring up a 10SI, is wiring package 1870921 (for those 6 to 12volt conversions). This contains the terminal connector AND an extra resistance wire pigtail to connect to the ignition system (don't use a ballast resistor if you use a resistance wire). Also available is an ammeter package (1965400).

Use a voltage guage to monitor your charging system. It will definately give you signs of impending problems. (Bad regulator, failing battery, etc.)

If your looking for a high output unit, keep an eye out for your everyday rebuilt (re-stamped 63amp). In my case, my rebuilt puts out 80amps at high rpm. More than enough for most needs.

High output aside, don't expect your alternator to do anything for you at idle speeds. Alternator output increases with rpm, even a 100amp unit won't put out much more than a 63amp unit at 1000rpm. If your using underdrive pulleys, this may highlight or worsen idle output problems.

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