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can you help me identify this alternator? Answered

I just got this alternator from my grandpa and am going to use it in a generator I'm working on but I Don't know what kind it is. He told me its a one wire but it has some prongs on the top. Any information is helpful and help is greatly appreciated.


Josehf Murchison

Best Answer 5 years ago

Well it is a Delco GM or Chevy alternator should be 12 volts and can go as high as 120 amps.

The black wire of your battery goes to the housing.

The red wire from the battery goes to the nut on the red insulator.

There are two types one with an external regulator and one with an internal regulator.

On the internal regulator alternator the two prongs go to the ignition one should go to the battery the other goes to the alternator indicator.

On the external regulator alternator the two prongs go to the 2 of the 4 prongs of the external regulator, the two other prongs on the regulator do the same as the internal regulator alternator.

If you can get the harness it would help.

You can get wiring diagrams by Googling:

"chevy alternator wiring diagram"

You should need a 3 Hp small engine to run it geared up 2:1 or more to about 3000rpm to 8000 rpm max.

On a wind mill you need to gear up the slow blades of the wind mill even more to power it.

harry88Josehf Murchison

Answer 5 years ago

So my grandpa was wrong its not a one wire? what is a safe resistance for the wire that starts the alternator at first I just want to replace it with a resistor.

Josehf Murchisonharry88

Answer 5 years ago

No resistor just a light and a switch.

Assuming the alternator is working and has an internal regulator the two prongs go to the ignition one should go to the battery the other goes to the
alternator indicator.

Most people wire it like this pic I would wire it with a double pole to cut power to both pins to prevent draining of the battery.


4 weeks ago

I need help with identity of this alternator. Its numbers didn't make it clear to me


10 months ago

What kind caf does this alternator go to


3 years ago

I realize this thread is 2 years old, but I have some information that wasn't posted by anybody else and it might help somebody with a similar question.

This is either a 10si or a 12si Delco alternator, most likely a 10si. Virtually all Delco alternators of this vintage have a model number stamped on the front case just behind the belt tension bolt "ear". You will see something like "1102454 63A", and below that something like "BF6 12NEG".

The first line is the specific model number and the "63A" is the rated output - in this case, 63 amps. These (virtually identical) alternators were rated differently for different applications, so you could see anything hovering around 60 amps plus or minus 20 or so. 12si units go past 100 amps.

The second line contains some sort of build code which probably means nothing to anybody but a Delco engineer, and the "12NEG", obviously, indicated 12 volt negative ground. I'm sure positive ground alternators exist - and will as long as England exists! - but I have never seen a Delco alternator so marked.

You can make this a "1 wire" alternator by making a simple short jumper wire with a female bayonet connector on one end and a post connector (large enough to fit on the BAT post) on the other. Plug the bayonet end onto the "2" terminal (may be marked "F") and the other on the BAT post. In a pinch, you can just wrap the wire around the "BAT:" post - I just like to be neat when fussing with electronics.

The "1" terminal (can be marked "R") is/was used to operate the idiot light in the dash board and can be ignored unless you want to rig an indicator light. The dash light was powered from the ignition "on" terminal and grounded by the alternator internal voltage regulator via the "1" terminal. When the alternator spools up and starts producing, +12v appears on the alternator "1" terminal and meets the +12v from the ignition switch and the light goes out.

The "2" terminal is used to "excite" the rotating magnetic field. Alternator rotors are not permanent magnets, they are electromagnets, and they need to be "jumped" at start up (aka "excited", or "bootstrapped" to computer people) in order to start generating electricity. Actually, there is usually SOME residual magnetism, and you can get alternators to self-energize by revving the engine past 3,000 rpm, but it isn't necessary as long as you have a battery in the circuit. The "2" terminal was usually connected to the "I" terminal on the solenoid (Ford-type solenoids) or the starter side of the Delco starter-mounted solenoid. This provided excitation current to the alternator field windings during startup. Virtually all automobile alternators are self-exciting once started, so this wire is not needed after startup - but there is no harm leaving it connected via the jumper I mentioned, since, in operation, all 3 of the terminals are "hot" with the alternator's operating voltage and only the "BAT" terminal is carrying any amperage.

Of course, if you want to complicate things, you can rig an indicator light via the "1" terminal and rig a push-button to "flash" the field after the motor starts...

If you are going to use this alternator with a home-brew power setup or backup generator for a battery-backed PV system, you are going to want a separate battery to excite the fields and that push-button might be necessary.


5 years ago

Certainly a car alternator - 12 volts most likely these days. You will need to turn it at 3000RPM to get any meaningful output though.