Alternator internal differences: What are they?

69427

69427

The Artist formerly known as Turbo84
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Mar 30, 2008
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Clinging to my guns and religion in KCMO.
Getting around to working on the (non) charging issue that showed up last weekend at the track. I'm currently debugging the harness end to eliminate that as a possible issue. While I was doing that, I got to thinking. If I have to eventually pull the alternator apart and replace the regulator or other parts (I was going to use one of my spare alternators for parts), why not just swap pulleys and use the other alternator. My original alternator is a 42 amp unit. The spare unit is a 63 amp. Just for kicks, what is the internal physical difference in these two alternators? I'm assuming the stator, but is the rotor different too?

Thanks,
Mike
 
In those chageover years for GM between the very early alts wired with EXternal regulators vs the later INternal regs....there was a HUGE ramp up increase in capabilities of the units....

I am going my memory, and it involves many cars from the GM lineup...not just vettes...

the early ones had the REGULATOR pins aligned ]] and were plugged into the backside of the alt/parallel with the front/rear of the car....they were very limited as to outputs ~50 amps, as most appliances were not a factory option....they were also very small diameter...minimal cooling capacity for extra thick wires, much less gaps....

the larger SI series from the smallest I know of...10SI through my larger diameter 17SI have the reg plugs arranged around the outer edge and going -- and so have internal regulator with some larger diameter and better cooling as a result...

that is about all I can help on the older units....

I did a 17SI upgrade off a '79 Seville with RW defogger rated 108 factory amps....due to electric fans...it works well....

:D
 
Well, the harness wires that feed the regulator look and measure okay. The Brown sense line goes hot when the key is on, and the Red exciter line is hot all the time. (Please correct me if I am wrong on what the electrical state of these wires should be.)
The first indication I had of an alternator issue was when I popped the hood after a track session and saw the exciter harness line broken out of the plastic "connector". I pushed the harness blade connector back into the plastic onto the reulator pin. The ammeter continued to show no positive charging, only the occasional discharge when I touched the brake pedal.
Looking at the internal connections for the regulator and field circuit, it seems to me that the alternator should run just fine even though this Red exciter line popped out of the connector. I would expect that the diode trio would supply the needed field current in the absence of the Red wire. Am I understanding this correctly?
I'm going to hook up a test circuit tomorrow to test out the regulator. I'm still drawing a blank on what could cause the alternator to fail just because the Red wire slipped out.
 
Simply, the 10SI alternators have different rotor/stator combinations for different output amps. AFIK, the regulator and diode sets are the same. I used to just swap the rotor/stator to the 100 amp models and be done.
 
TimAT said:
Simply, the 10SI alternators have different rotor/stator combinations for different output amps. AFIK, the regulator and diode sets are the same. I used to just swap the rotor/stator to the 100 amp models and be done.
Click to expand...

The unit I have had on my '72 here for some 15 years is a 17SI, it is factory rated at 108 amps, and is maybe a inch larger diameter with same mounting as another of the SI series....it's off a '79 Seville with Rwindow defogger.....one of my typical junkyard finds.....I dunno about the internal regulators being any different at all, they MAY be....

I know there are 10 and 12 in the series, but other than being smaller diameter than mine, I have no idea about the variations in amp ratings, or even if they can do better/worse than mine....

I look at it that my larger diameter unit certainly has better air flow for cooling, more room inside, and mounted in the typical C4 location above the headers, it needs as much airflow as can be gotten....

one of the problems with the newer CS series was inadequate cooling, they did have higher output at idle, but that tighter coupling and smaller diameter meant inferior cooling....problems....

supposedly solved by the CS144 series....I dunno, never owned one....

In spite of all the 'arguement' over 'there' through the years, MY 17SI works, so I leave well enough alone, besides I have a lifetime warrenty from years ago through AZone......:D:chinese:
 
TimAT said:
Simply, the 10SI alternators have different rotor/stator combinations for different output amps. AFIK, the regulator and diode sets are the same. I used to just swap the rotor/stator to the 100 amp models and be done.
Click to expand...

The stator I understand, since the winding difference gives the added amperage. The rotor stumps me, since all it does is supply a rotating field, with very little current needed.
 
I agree. Years ago the Chevy parts catalog listed different part numbers for both the rotor and stator different applications. I assumed that they were both different. Maybe incorrectly, but that was how they listed them.
 
TimAT said:
I agree. Years ago the Chevy parts catalog listed different part numbers for both the rotor and stator different applications. I assumed that they were both different. Maybe incorrectly, but that was how they listed them.
Click to expand...

I a tad unsure about that rotor strength thing, in that increasing the amount of poles on the field/stator would more effective use the peaks of the field to good use, and decrease the 'down time' at any given RPM.....I"m unsure now much playing with the rotor/magnet would actually affect the final output....surely some regulator could put a tad more volts into the given coil and make a25% stronger field, I would assume,....trick is....I dunno what affect it has on final power capabilities....surely there is NO free ride there, and has to be some tradeoff, or Burnie will make off.....

:smash::eek::lol:
 
No deal here, but I just dug up my GM parts catalog from my archives. For the "Y" body (Corvette) there are listed 3 different rotors and 6 different stators by GM part numbers. Do a little mix and match from all the different cars and trucks that were available in the 68-82 years and I'll bet there are a big pile of different ones.
 
TimAT said:
No deal here, but I just dug up my GM parts catalog from my archives. For the "Y" body (Corvette) there are listed 3 different rotors and 6 different stators by GM part numbers. Do a little mix and match from all the different cars and trucks that were available in the 68-82 years and I'll bet there are a big pile of different ones.
Click to expand...

Tim, any clue as to what in FUCK was on their minds with doing a mishmash of crap like that??? sounds to me like a patch on top of a patch cause NO WAY IN HELL any 'economies of scale' in manufacturing can take place with that kind of silliness going on.....I only knew of 10-12-17 SI alts, and ASSumed they were all the same internally for any given number.....I know some were marked for different cars...I figgered just for assy work....so a Caprice wouldn't get a Caddy alt or whatever for accessory ratings....

I guess I make it too simple, I would have gone for 100 amp alts across the board, and bag all that complicated shit....

:gurney:
 
No idea! But I suspect that it was cheaper to build 300k 43 amp models than 600k 100 amp ones. And why put a 100 amp alternator on a 4 cylinder, no air, no nothing Nova? It'd take more HP to run the alternator than the iron duke made. And an autobox behind that. Back in the day, a VEGA with an auto and air would downshift when the A/C compressor cycled on going up a hill. Throw a 100 amp on that and you could walk faster going uphill? But take a 472 Cube Caddy, with power everything, and more lights than Las Vegas, 43 amps, man, it'd get dark when you stepped on the brake.

I'll be willing to bet that GM wasn't the only one that did it that way either.
 
TimAT said:
No idea! But I suspect that it was cheaper to build 300k 43 amp models than 600k 100 amp ones. And why put a 100 amp alternator on a 4 cylinder, no air, no nothing Nova? It'd take more HP to run the alternator than the iron duke made. And an autobox behind that. Back in the day, a VEGA with an auto and air would downshift when the A/C compressor cycled on going up a hill. Throw a 100 amp on that and you could walk faster going uphill? But take a 472 Cube Caddy, with power everything, and more lights than Las Vegas, 43 amps, man, it'd get dark when you stepped on the brake.

I'll be willing to bet that GM wasn't the only one that did it that way either.
Click to expand...

Tim, the alt supplies only what the loads demand, no more than that....

which is at the crux of my rant....surely a wimpy alt can be overload, that's certainly true....but think of the killer stereo some Vega owner could have had....:pprrtt:

:shocking:
 
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