If open circuit voltage is 12.4 volts and the system voltage with the engine running is also 12.4 volts, what does this indicate?

If open circuit voltage is 12.4 volts and the system voltage with the engine running is also 12.4 volts, what does this indicate?

• A. The charging system isn't working
• B. The charging system is functioning and charging the battery
• C. The battery is in perfect condition
• D. The engine speed is too low

Answer: (A)

When the engine is running, the charging system should push the system voltage well above the battery’s resting voltage to keep the battery charged. An open-circuit voltage of 12.4 V means the battery is not fully charged but has some charge. If the system voltage stays at 12.4 V once the engine is running, the alternator isn’t charging the battery. That indicates the charging system isn’t functioning properly. Possible reasons include a slipping or broken belt, a bad alternator, a faulty voltage regulator, or wiring/fuse issues that prevent charging. The idea isn’t that the battery is perfect or that engine speed is too low; rather, there’s no charging happening, so the charging system isn’t working.

When the engine is running, the charging system should push the system voltage well above the battery’s resting voltage to keep the battery charged. An open-circuit voltage of 12.4 V means the battery is not fully charged but has some charge. If the system voltage stays at 12.4 V once the engine is running, the alternator isn’t charging the battery. That indicates the charging system isn’t functioning properly.

Possible reasons include a slipping or broken belt, a bad alternator, a faulty voltage regulator, or wiring/fuse issues that prevent charging. The idea isn’t that the battery is perfect or that engine speed is too low; rather, there’s no charging happening, so the charging system isn’t working.