voltage regulator

Regulators control the field current, not the output current. The field current typically averages to be a few amps. A later style regulator that uses the square back alternator uses N-channel device to switch current, the early single field connection use a P-channel device, it is inherently weaker.

Regulators are quite rugged, but can fail when driven with a failed battery such as shorted or open cell, failure of alternator diodes, jump starting with engine running, poor ground or other connections intermittent.