good reply.
The cut in and out can also be due to poor bat cable connections- clean and desulfate the connections completely. Bad connection can also cause lack of charge of bat. could also be a bad ground twixt bat/frame/body/engine or alternator/engine/frame/body.
Nemo - if resoldering (rewetting)a joint - always make sure to also use flux to cleanup oxidation on the copper parts being soldered together.
Voltage regulators are built into alternators now. They used to be standalone (outside alternator) items.
Four alternators in 217k miles is very excessive. Try higher quality parts (either dealer or stores like NAPA). Autozone carries fairly cheap parts, imo.
Another possible cause of the bat going bad- freezing weather on a discharged battery. 'Since Feb' is a long time in cold weather. Nothing can destroy a battery faster than freezing weather on a dead battery. KEEP 'EM CHARGED- even a tiny trickle charge will keep them in good shape.
Nemo is correct about the voltmeter test. Also check the bat with engine not running. 10v indicates one cell is dead - 8v is two and so on. Anything above 15 volt charging indicates a shot regulator, and will kill the bat quickly. Also check for AC current - if you get an AC reading (depending on the meter) - uou've got shot diodes - replace alternator.
Finally, brethren, whatsoever things are true, whatsoever things are honest, whatsoever things are just, whatsoever things are pure, whatsoever things are lovely, whatsoever things are of good ...
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