Firetrol AS‑2001 is a fully automatic 4‑step battery charger (12 V or 24 V DC) that accepts 115 / 230 VAC input and uses a 3AG/6A 250 V AC fuse and 3AB/20A 250 V DC fuse. Known failure modes include a “missing or defective battery” fault during the qualification stage (LEDs flash yellow/green), blown AC/DC fuses, stuck charging‑stage relays, and internal controller board faults that cause no LED indication or continuous charging. First‑check diagnostics: verify incoming AC voltage and confirm the AC fuse is intact; inspect the DC output for correct voltage and continuity of the battery terminals; review the charger’s LED status sequence for fault codes (e.g., yellow/green flashing indicates a battery issue).[oss-gpt-20b]