Component Tests and General Diagnostics

If the battery tests good but still fails to perform satisfactorily, the following are some of the more common causes:
^ A vehicle accessory was left on overnight.
^ The driving speeds have been slow with frequent stops (stop-and-go driving).
^ The electrical load has exceeded the generator output (particularly with the addition of aftermarket equipment).
^ Existing conditions in the charging system, including the following possibilities:
- An electrical short
- A slipping belt
- A bad generator
- A bad generator voltage regulator
^ The battery has not been properly maintained, including the following situations:
- A failure to keep the terminals tight
- A failure to keep the terminals clean
- A loose battery hold-down
^ Existing mechanical conditions in the electrical system, such as any short or pinched wires, attributing to power failure.
^ The car is in storage for extended periods of time.
^ Plug fouling, causing extended cranking periods.
^ The hydrometer has been read incorrectly.
^ There has been an insufficient Ampere-hour charge rate for a discharged battery.
^ There is a burned out charge indicator bulb causing a NO CHARGE condition.
^ There is a continuous current draw on the battery through excessive parasitic drain.
^ The battery is old.