POwermaster 140A alternator - is it going bad?

I have a powermaster 140 amp one-wire alternator, with a 4 gauge lead running right to the battery. The other day, the volts were fine at idle. but when i went to pull out, they went up to about 16 v at under 2k rpm. so i turned everything on (headlights, wipers, a/c, electric cooling fan) to keep the voltage down until i got home. volts went down to about 12.7. by the time i got home, it would overcharge with everything still on. i let it sit for 30 minutes and started it back up and it was fine...so i replaced the 4 ga charge lead since it looked like the insulation was receding from the terminals. oh, and when it was hot it was kind of limp feeling.

so, is this a regulator problem inside the alternator, or is it just a badly made cable?

no its an internal regulator...apparently the powermaster is a gm unit converted to one wire operation, but it fits the ford mounting bracket.

i thought since it only did it after it was hot, it was voltage drop in the cable, and the regulator was trying to make up for the drop by raising the voltage

yeah they are self-exciting...and i guess the point of having a one wire alt is to only have one wire (lol) so it senses battery voltage through the output wire instead of the little green wire. thats probably not the best setup as far as reliability goes, as ive found out, but maybe im just not good at crimping terminal ends.