1. Check your existing alternator: The easiest way is to look at the alternator itself. The amperage rating (e.g., 65 amps, 80 amps, 105 amps) will be stamped on it. This is the most accurate method.
2. Consult your owner's manual: Your owner's manual should specify the correct alternator size for your specific Beretta's engine and options.
3. Use a parts lookup website or your local auto parts store: Websites like AutoZone, Advance Auto Parts, or Napa Auto Parts allow you to search by your vehicle's year, make, model, and engine size to find the correct alternator. Your local parts store can also assist you with this.
Without knowing your specific engine (e.g., 1.8L, 2.3L), it's impossible to give you a definitive answer. Providing this information will greatly help in identifying the correct alternator size.