That's not an alternator- - - -it's a 12 volt DC generator. There will also be a regulator mounted somewhere in the engine compartment, a rectangular box about 3 by 4 inches, about 3 inches tall, with 3 wires attached to it. You'll need to figure out whether the generator, the regulator, or the wiring (or any combination thereof) is the actual problem. I'd strongly suggest getting some professional help, since calling the item in your photo an "alternator" speaks volumes about your experience with older charging systems. The first thing I'd suggest would be to disconnect, clean, and reinstall all the wires, AFTER disconnecting both battery cables. Short circuits destroy wiring harnesses, and sometimes entire vehicles, in a big hurry!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!