What voltage range indicates normal alternator performance when the engine is running under load?

• A. 11.5–12.5 V
• B. 12.0–13.0 V
• C. 13.0–13.5 V
• D. 13.8–14.8 V

Answer: (D)

Under load, the charging system must push the voltage up to roughly 13.8–14.8 volts to both run the vehicle’s electricals and recharge the battery. This higher voltage overcomes the battery’s internal resistance and keeps the battery charging while the engine and accessories are drawing current. Battery voltage at rest sits around 12.6 volts, so readings in the low 12s or below during operation indicate undercharging. A range around 13.0–13.5 V may be marginal, but the normal, healthy charging condition under load is closest to 13.8–14.8 V, which is why that option is correct.