If the charging system warning light is on, plan to stop driving soon. Once the battery runs down, the vehicle will lose power and stall.
What charging failure means
The charging system maintains the battery and runs all electrical accessories while the engine is on. When it fails, the vehicle slowly drains the battery instead of charging it. The result is a warning light and, eventually, a stall.
Common causes
Alternator wear or internal diode failure, often producing low output or voltage ripple.
Voltage regulator failure, which causes over- or undercharging.
Broken, glazed, or slipping drive belt, which prevents the alternator from spinning correctly.
Corroded or loose battery cables, which act like a charging system failure even when the alternator works.
Failing battery that cannot accept or hold a charge.
How AAB Service tests
Resting battery voltage and load test on the battery.
Alternator output at idle and under load.
Voltage ripple analysis to find diode failure.
Cable, ground, and parasitic draw testing when needed.
San Antonio auto repair
Have a vehicle-specific question?
AAB Service can inspect, test, and explain what is happening with your vehicle so you can decide what to do next.