I've been working on some of these rebuild mysteries and this is may be the source of many problems.
Remember way back I said that it seemed like the regulators failed when using a revised squareback?
I was talking about the transistorized ones that look like the Mopar Performance regulator. Standard's tech person couldn't tell me anything about its specs but it I'm more convinced now that most of the regulators weren't made to handle field currents over 5 amps.
It looks to me like alternator rebuilders use just one rotor for replacement. The current draw on my 10 yr old Carquest 7024 was just over 5 amps. I figured the rotor was bad. But looking at the alternator sheet
@Dana67Dart posted, looks like this may be typical for rebuilds. :(
They're using a rotor wound with bigger wires or whatever that is lower resistance and higher draw.
I think this may be the root of many problems we're seeing. Its killing the VRs, and its almost doubling the load on the wiring. Most A-bodies only got an 18 ga wire to the regulator, and maybe the same to the field. My point is now those 18 ga crimps are subject to 5-6 amps or more instead of 2 to 3 amps. Not even getting into what that might be doing to the mechanical regulators.
Maybe I'm jumping to conclusions but wanted to share so you guys can look out for this.
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from the '73 FSM.
Slip ring to slip ring the rotor should be 3 to 4 ohms at room temperature.
The rotor in Carquest 7024 sq back measured 1.7 ohms. This drew 5.6 amps at 12.5 Volts when tested on the car per FSM. It had one bad diode - not sure that magnetic field makes much of a difference but I will retest when its back together.
The rotor in the Tuff Stuff Revised Swq back: 1.7 Ohms
Rotor in a '70-71 alternator, Reliant 7015 rebuild from junkyard 22 years ago: 3.5 ohms
NOS late 60s rotor: 3.7 Ohms