Change a fan belt on 903 cinquecento?

To change the fan belt on a Fiat 903 Cinquecento, first, ensure the engine is cool and disconnect the battery for safety. Loosen the tensioner by turning the adjuster bolt, then remove the old belt from the pulleys. Install the new belt, ensuring it is properly aligned with all pulleys, and then re-tighten the tensioner to secure it. Finally, reconnect the battery and start the engine to check for proper operation.