What fools people
- The alternator looks healthy at idle with little load.
- Charging drops once refrigeration, autopilot, and house-bank demand show up together.
- Crews replace the alternator before checking the voltage path.
First checks to run
- Measure voltage at the alternator output stud and again at the battery bank under the same load.
- Inspect belt condition, tension, dust, glazing, and pulley alignment.
- Verify regulator settings and temperature compensation assumptions.
Likely causes
- Cable loss or poor lugs between alternator and bank.
- Regulator misconfiguration for the battery chemistry.
- Heat derating or airflow issues around the alternator.
When it is urgent
- Burning smell, belt dust, or visible heating.
- Charging voltage climbing out of bounds.
- Alternator or regulator behavior changing rapidly between runs.
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