it has a inbuilt regulator
it doesn't have one the alternator is regulated in side
Inside the alternator. Replacing it requires careful disassembly of the rear shell and then soldering the new unit in place. Best for persons with experience.
The alternator is overcharging due to the regulator malfunctioning. Replace the alternator.
The easiest way to check any alternator in a car is to have the vehicle running and use a VOLT meter to read across that battery terminals. The voltage should be in the range of 13.4 volts to 14.5 volts..no lower, no higher. If either low voltage or high voltage exist, that alternator is probably defective.
Remove the wiring harness from your 1990 Subaru alternator. Remove the alternator belt. Remove the alternator retaining bolts. Reverse the process to install your new alternator.
The oil sending unit on a 2002 wrx subaru is almost under the alternator. I suggest you remove the alternator and it is easier to remove the oil sending unit.
top of front of engine, under alternator
Directly below the alternator on the block.
There should be a bolt attached to the alternator that should work.
Danger High Voltage
Schucks has one with a lifetime warrantee for $123.99. Subaru dealership tried to charge me up to $600 for a factory part.
It is located under the alternator.