the regulator with 3 relays is for a generator
the extra relay will connect the output of the generator to the battery when the generator has voltage on its output
alternator doesnt need this it has diodes that do the same thing.
But the alternator is always connected to the battery thru the diodes.
This is why theres a fuseable link (diodes can fail to a short)
the other two relays the one with very fine wire senses the battry voltage and will stop the charge at 14v or so.
the one with the larger wire feeds more voltage to the feild if the output tapers off.
these regulators very rarly fail and can usually be ajdusted for more or less charge or voltage.. the real old one have screws for adjustments.. the newest youve got to bend the tabs on the springs and contacts.
To fix these a point file and a burnishing tool is all thats required.
to fix a new electronic one a trash can and a new part is the only way possible. they are sealed and potted.
alternators have only brushes and bearings as moving parts they can be fixed with either of these.
older alternators have diodes that can be replaced and an external regulator( sometimes the relay kind)
newer alternators may be an all in one (brush diode electronicpack) that can be replaced as a unit.