Charging fault diagnosis and response
Charging faults develop silently: watch the ammeter continuously, not only when something feels wrong (TP 1102).
| Fault | Ammeter shows | Meaning | If uncorrected |
|---|---|---|---|
| Excessive rate of charge | Sustained high charge, above normal steady value | System voltage may be higher than normal (overvoltage) | Can damage electrical components and overheat the battery, boiling off its electrolyte |
| Insufficient rate of charge | No charge, or discharge | Battery alone supplies the load | Battery will drain |
Excessive rate of charge:
- Follow AFM checklist; do not let it continue.
Insufficient rate of charge:
- Needle on - side (discharge) = battery supplying the load: alternator not producing (likely failed).
- Discharge = battery draining, not charging.
- Full-scale minus deflection on centre-zero ammeter = same reading: alternator/generator malfunction (PHAK ch.7).
- Charge warning light (if fitted): illuminates when alternator faulted and shut down. Otherwise ammeter is only cue.
- Alternator off: entire electrical load on the battery.
Response:
- Turn off all nonessential electrical equipment (extra lights, radios) to conserve battery (PHAK ch.7).
- Tell ATC in case radio is lost before landing.
Generator-equipped aircraft: check charge rate at run-up. Discharge later in flight: same shed-load response.
Trap: a sustained high charge is not "extra charging"; it is a fault that can signal overvoltage and cook the battery.
References
- TP 1102 (Flight Training Manual), Electrical Problems
- FAA-H-8083-25 PHAK ch.7 (Electrical System)