[JohnFromVentura]

Getting ready to add after market air cond. to my 63 and first and need to change my 37 Amp alternator to a 100+ amp. Wondering about the physical differences between 10Si and 12Si units. I have read through the MAD papers and realize that the 12Si has better cooling but not sure if the the 12Si is the same actual size as my old 37 Amp Alt?. Aftermarket 100+ amp Alts seem to come in both 10Si and 12Si housings but probably going to use the 1 wire approach with a volt meter. Thanks for any help, John!

[JSPONT]

This is a 1 wire 10 si. I liked the small size, had my alternator guy put a 115 amp stator.

[Bill Hanlon]

One wire alternators regulate voltage at the output lug of the alternator. A properly installed 3 wire alternator regulates to voltage sensed from somewhere in the dash, which could be a volt or so less than the output of the alternator. I've had both and prefer the 3 wire. I converted the 1 wire system in my current ride to 3 wire and was rewarded with brighter headlights.

[Stuart]

Do you really need an alternator that's over 100 amps? Kind of seems like overkill, unless you also have a megawatt stereo or other high current loads. I'm not a fan of one wire alternators either, it seems the only benefit is two less wires and if it fails you're not going to be able find a replacement at the local auto parts store.

[JSPONT]

Originally Posted by Stuart

Do you really need an alternator that's over 100 amps? Kind of seems like overkill, unless you also have a megawatt stereo or other high current loads. I'm not a fan of one wire alternators either, it seems the only benefit is two less wires and if it fails you're not going to be able find a replacement at the local auto parts store.

With electric fans, radio and amp, msd, a/f gauge and other electronic controls, yes the amps are needed. If you run a bone stock car I guess it would not be needed. Stock is not my thing.

[JohnFromVentura]

Bill, I'm leaning towards the 3 wire alternator. MAD doesn't seem to answer their phone and might not be in business? I'm wondering how you wired your car? Does the white wire on the right have the diode and get connected to the + side of the coil (or another place) and the left blue wire go to a dash light if one exists? There a lot of conflicting videos on utube so little confused here! Also does someone besides MAD sell the 3 wire kit?
Thanks, John

Originally Posted by Bill Hanlon

One wire alternators regulate voltage at the output lug of the alternator. A properly installed 3 wire alternator regulates to voltage sensed from somewhere in the dash, which could be a volt or so less than the output of the alternator. I've had both and prefer the 3 wire. I converted the 1 wire system in my current ride to 3 wire and was rewarded with brighter headlights.

[Bill Hanlon]

I wired the output (the big lug on the back) directly to the battery wire on the starter.

Let's call the two terminals on the back edge 1 and 2. My alternator mounts with 1 and 2 in the 12 o'clock position. 1 is towards the driver's side of 2.

Terminal 2 is the "voltage sense" connector. I wired mine directly to the electric choke connection that was physically just a few inches away, but quite a few feet away electrically as the choke wire came from under the dash and is only hot when the ignition switch is in the "run" position. Connect yours to somewhere that is only hot with the key on. Do not connect it to the output of the alternator as many places on the internet suggest. Doing that effectively turns it back into a 1 wire alternator asw far as regulation goes.

Terminal 1 connects through a diode or idiot lamp to 12 volts that is only on when the key is in the "run" position. I used a 12V LED (both a lamp and a diode) that was less than $5 at FLAPS.

[JohnFromVentura]

I got my 100 amp, 3 wire alternator working great. There is a lot of bad information on the internet on this but thanks to our forum member Bill Hanlon for putting me on the right track. See the attached picture for my wiring. I used a 1N5402 Diode that I bought on ebay for a few dollars ... I have 20+ extras so let me know if you need one? Also, it is hard to solder the heavy diode leads to thinner 16 gauge wire, I used NAPA solder filled butt connectors, a decent soldering iron and shrink sleeving. John