Stock alternator amp rating
08-25-2020, 12:20 PM
#4
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Re: Stock alternator amp rating
There were quite a few "ratings" for alternators back then. Most of the ones for the more optioned ones of these cars were "rated" at around 100 amps. Cars with AC, power windows/seats/etc., rear window defogger, and other high-power accessories, got those. Cars without so much of that got ones as low "rated" as 60 - 70 amps.
Problem is, the "rating" is stamped on an aluminum casting that has NOTHING WHATSOEVER to do with anything electrical; and ALL electrical parts are interchangeable into ALL cases no matter what "rating" is stamped on them.
Ponder the implications of that for a minute while I tell you what goes on inside an alternator rebuilder.
They take the alternators apart and put the parts all together for all of them in some manner appropriate to each part, and clean them up. Cases and fronts probably go in a giant wire-mesh ******* kind of thing to go to a parts washer with some substance that etches paint and corrosion and labels and whatnot off of them. Armatures (rotors) would get arranged in some manner other than a giant bin or pile, like maybe a fixture that makes little cradles for them or has holes that the shaft can stick into (hehehe) or something along those lines, then go into a MUCH gentler parts cleaning setup of some sort. Stators go their own way similarly to armatures but of course physically different since they're a different shape and size. Brush holders probably go in the trash; bridges into an electrical cleaner; regulator, diode trios, and resistors, might get cleaned or thrown away.
Then after they're all cleaned up and certain other prep steps have been taken (like sanding the commutators on the rotors for example), somebody picks up "a" rotor, "a" stator, "a" case, "a" front, "a" regulator, "a" brush holder, "a" bridge, etc. etc. etc., and assembles them into an alternator.
Now... do you suppose they have ANY IDEA whether the rotor and stator, which are the parts that determine the output amps, go with the stamping on whatever case they put them into? In what I've seen, NOT.
Meaning, if you have a rebuilt alternator, ALL BETS ARE OFF as to what its ACTUAL capacity is. But odds are VERY HIGH that is is not related in any manner way shape form or fashion to the stamping on the case.
That said, if you have a bunch of alts you can take apart and LOOK AT THE PARTS, you'll see right away how different they can be. The parts that matter to capacity are the stator, where the larger the wire size it's wound from (AFAIK they all have the same # of turns), the higher it is; and the rotor, which is harder to characterize, because it's a combination of the wire size and the # of turns of wire that it's would with. The magnetic steel might be different but that would be much harder to measure. If you had a whole pile of parts, you could pick and choose the stator relatively easily, and then pass current through the rotors and find the one that produces the strongest magnetic field which would be a bit more difficult but not impossible. Then you could build yourself the best alt possible.
Using a larger gauge alt wire is a good idea, subject to, that it's MUCH easier to destroy the alt or set the car on fire by an electrical catastrophe, unless you retain the appropriate fusible link size.
Problem is, the "rating" is stamped on an aluminum casting that has NOTHING WHATSOEVER to do with anything electrical; and ALL electrical parts are interchangeable into ALL cases no matter what "rating" is stamped on them.
Ponder the implications of that for a minute while I tell you what goes on inside an alternator rebuilder.
They take the alternators apart and put the parts all together for all of them in some manner appropriate to each part, and clean them up. Cases and fronts probably go in a giant wire-mesh ******* kind of thing to go to a parts washer with some substance that etches paint and corrosion and labels and whatnot off of them. Armatures (rotors) would get arranged in some manner other than a giant bin or pile, like maybe a fixture that makes little cradles for them or has holes that the shaft can stick into (hehehe) or something along those lines, then go into a MUCH gentler parts cleaning setup of some sort. Stators go their own way similarly to armatures but of course physically different since they're a different shape and size. Brush holders probably go in the trash; bridges into an electrical cleaner; regulator, diode trios, and resistors, might get cleaned or thrown away.
Then after they're all cleaned up and certain other prep steps have been taken (like sanding the commutators on the rotors for example), somebody picks up "a" rotor, "a" stator, "a" case, "a" front, "a" regulator, "a" brush holder, "a" bridge, etc. etc. etc., and assembles them into an alternator.
Now... do you suppose they have ANY IDEA whether the rotor and stator, which are the parts that determine the output amps, go with the stamping on whatever case they put them into? In what I've seen, NOT.
Meaning, if you have a rebuilt alternator, ALL BETS ARE OFF as to what its ACTUAL capacity is. But odds are VERY HIGH that is is not related in any manner way shape form or fashion to the stamping on the case.
That said, if you have a bunch of alts you can take apart and LOOK AT THE PARTS, you'll see right away how different they can be. The parts that matter to capacity are the stator, where the larger the wire size it's wound from (AFAIK they all have the same # of turns), the higher it is; and the rotor, which is harder to characterize, because it's a combination of the wire size and the # of turns of wire that it's would with. The magnetic steel might be different but that would be much harder to measure. If you had a whole pile of parts, you could pick and choose the stator relatively easily, and then pass current through the rotors and find the one that produces the strongest magnetic field which would be a bit more difficult but not impossible. Then you could build yourself the best alt possible.
Using a larger gauge alt wire is a good idea, subject to, that it's MUCH easier to destroy the alt or set the car on fire by an electrical catastrophe, unless you retain the appropriate fusible link size.
Last edited by sofakingdom; 08-25-2020 at 12:32 PM.
08-25-2020, 05:22 PM
#5
Junior Member
Thread Starter
Re: Stock alternator amp rating
There were quite a few "ratings" for alternators back then. Most of the ones for the more optioned ones of these cars were "rated" at around 100 amps. Cars with AC, power windows/seats/etc., rear window defogger, and other high-power accessories, got those. Cars without so much of that got ones as low "rated" as 60 - 70 amps.
Problem is, the "rating" is stamped on an aluminum casting that has NOTHING WHATSOEVER to do with anything electrical; and ALL electrical parts are interchangeable into ALL cases no matter what "rating" is stamped on them.
Ponder the implications of that for a minute while I tell you what goes on inside an alternator rebuilder.
They take the alternators apart and put the parts all together for all of them in some manner appropriate to each part, and clean them up. Cases and fronts probably go in a giant wire-mesh ******* kind of thing to go to a parts washer with some substance that etches paint and corrosion and labels and whatnot off of them. Armatures (rotors) would get arranged in some manner other than a giant bin or pile, like maybe a fixture that makes little cradles for them or has holes that the shaft can stick into (hehehe) or something along those lines, then go into a MUCH gentler parts cleaning setup of some sort. Stators go their own way similarly to armatures but of course physically different since they're a different shape and size. Brush holders probably go in the trash; bridges into an electrical cleaner; regulator, diode trios, and resistors, might get cleaned or thrown away.
Then after they're all cleaned up and certain other prep steps have been taken (like sanding the commutators on the rotors for example), somebody picks up "a" rotor, "a" stator, "a" case, "a" front, "a" regulator, "a" brush holder, "a" bridge, etc. etc. etc., and assembles them into an alternator.
Now... do you suppose they have ANY IDEA whether the rotor and stator, which are the parts that determine the output amps, go with the stamping on whatever case they put them into? In what I've seen, NOT.
Meaning, if you have a rebuilt alternator, ALL BETS ARE OFF as to what its ACTUAL capacity is. But odds are VERY HIGH that is is not related in any manner way shape form or fashion to the stamping on the case.
That said, if you have a bunch of alts you can take apart and LOOK AT THE PARTS, you'll see right away how different they can be. The parts that matter to capacity are the stator, where the larger the wire size it's wound from (AFAIK they all have the same # of turns), the higher it is; and the rotor, which is harder to characterize, because it's a combination of the wire size and the # of turns of wire that it's would with. The magnetic steel might be different but that would be much harder to measure. If you had a whole pile of parts, you could pick and choose the stator relatively easily, and then pass current through the rotors and find the one that produces the strongest magnetic field which would be a bit more difficult but not impossible. Then you could build yourself the best alt possible.
Using a larger gauge alt wire is a good idea, subject to, that it's MUCH easier to destroy the alt or set the car on fire by an electrical catastrophe, unless you retain the appropriate fusible link size.
Problem is, the "rating" is stamped on an aluminum casting that has NOTHING WHATSOEVER to do with anything electrical; and ALL electrical parts are interchangeable into ALL cases no matter what "rating" is stamped on them.
Ponder the implications of that for a minute while I tell you what goes on inside an alternator rebuilder.
They take the alternators apart and put the parts all together for all of them in some manner appropriate to each part, and clean them up. Cases and fronts probably go in a giant wire-mesh ******* kind of thing to go to a parts washer with some substance that etches paint and corrosion and labels and whatnot off of them. Armatures (rotors) would get arranged in some manner other than a giant bin or pile, like maybe a fixture that makes little cradles for them or has holes that the shaft can stick into (hehehe) or something along those lines, then go into a MUCH gentler parts cleaning setup of some sort. Stators go their own way similarly to armatures but of course physically different since they're a different shape and size. Brush holders probably go in the trash; bridges into an electrical cleaner; regulator, diode trios, and resistors, might get cleaned or thrown away.
Then after they're all cleaned up and certain other prep steps have been taken (like sanding the commutators on the rotors for example), somebody picks up "a" rotor, "a" stator, "a" case, "a" front, "a" regulator, "a" brush holder, "a" bridge, etc. etc. etc., and assembles them into an alternator.
Now... do you suppose they have ANY IDEA whether the rotor and stator, which are the parts that determine the output amps, go with the stamping on whatever case they put them into? In what I've seen, NOT.
Meaning, if you have a rebuilt alternator, ALL BETS ARE OFF as to what its ACTUAL capacity is. But odds are VERY HIGH that is is not related in any manner way shape form or fashion to the stamping on the case.
That said, if you have a bunch of alts you can take apart and LOOK AT THE PARTS, you'll see right away how different they can be. The parts that matter to capacity are the stator, where the larger the wire size it's wound from (AFAIK they all have the same # of turns), the higher it is; and the rotor, which is harder to characterize, because it's a combination of the wire size and the # of turns of wire that it's would with. The magnetic steel might be different but that would be much harder to measure. If you had a whole pile of parts, you could pick and choose the stator relatively easily, and then pass current through the rotors and find the one that produces the strongest magnetic field which would be a bit more difficult but not impossible. Then you could build yourself the best alt possible.
Using a larger gauge alt wire is a good idea, subject to, that it's MUCH easier to destroy the alt or set the car on fire by an electrical catastrophe, unless you retain the appropriate fusible link size.
Mike
08-26-2020, 10:07 PM
#6
Member
Re: Stock alternator amp rating
My 1985 IROC 305 TPI came with a 108 amp factory rating per the RPO list and the same stamped on the housing. The parts book shows an optional 120 for this application (Vin "F"). I don't know what options would drive the 120 amp version. About the only electric options that mine doesn't have is rear wiper and a power seat
08-27-2020, 05:51 PM
#7
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Re: Stock alternator amp rating
AFAIK the factory used the same gauge wire in all of em. Too much trouble (read: EXPENSE) to try to cheeeeeeepen the cheeeeeeeeper cars further by using a slightly smaller wire gauge for a 2' piece of wire; then having to keep track of stocking 2 different part #s each of which turns over only a fraction of what their COMBINED turnover rate is.
Last edited by sofakingdom; 08-27-2020 at 05:57 PM.
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