Alternator 66-78 with external regulator Fiat 124 Spider, 124 Coupé

The Fiat 124 Spider, manufactured from 1966 to 1978, comes standard with an alternator equipped with an external voltage regulator. When the engine is running, the charging voltage at the battery should be between 13.8 and 14.4 volts. A voltage of 13.6 to 14.2 volts is normal when the engine is idling.

Guidelines:

• Engine off: 12.4–12.8 V
• No-load: 13.6–14.2 V
• 2,000–3,000 rpm: 13.8–14.4 V

Attention:

• Below 13.5 V at high RPM → The battery is not charging sufficiently. Possible causes include a faulty voltage regulator, worn-out carbon brushes, a faulty alternator, or poor cable or ground connections.
• Over 14.8 V → The voltage regulator is likely defective, and the battery may become overcharged.

Tip: The charging voltage is always measured directly at the battery terminals —not at the alternator. This is how you get the most accurate measurement.