Help Alternator ? Options

[bdog_v]

Hello I have a 94 celica gt while idling at night with the lights on heater on and rear defroster the lights will dim and the battery warning light will come on.
I believe the alternator is dieing. It only happens at idle and it comes and goes. I'd like to get it fixed before it leaves me stranded somewhere.
I am wondering?
-Is there a voltage regulator somewhere outside of the alternator or is it internal? I don't want to replace the alternator when it could be something else that regulates voltage.

-Also where is the best place to get an alternator for this beast? Usually these foriegn alternators go for over $100 bones yikes....


Thanks guys...

[bdog_v]

Well I price alternators today ranging from $144 to 215 but they all list a 70 and 80 amp alternator and I don't know which one I have its in a 94 2.2liter gt. How do you tell? Thanks....