The controller logs a 'Charger Fault' or 'Battery Charger Failure' alarm; battery voltage slowly drops over days.

Safety: Turn off AC power feeding the charger and disconnect the battery negative cable before servicing.

• Verify AC supply: Check the breaker or fuse feeding the charger from the utility panel. Restore power if tripped.
• Inspect charger fuse: Many Generac chargers have an internal fuse. Remove the charger cover (if serviceable) and test/replace the fuse as needed.
• Measure charger output: With AC power on and the battery connected, measure DC voltage at the battery. If it is not in the 13.2–13.6 V range, replace the charger module with the correct Generac part.
• Check connections: Tighten charger output terminals and clean any corrosion.