R-Pro › Field cases › Air conditioning
BLDC Outdoor Fan Motor Burnout (Bearing Wear → Overcurrent Trip)
Likely causes
Bearing wear → increased rotational resistance → winding overcurrent → burnout
Check: Power off, manually rotate fan blade — stiffness or rattling indicates bearing failure. Measure 3-phase winding resistance (all phases should be equal; >10% difference indicates winding degradation).
What to do: Replace bearing unit (verify 6202/6203 spec). If winding is burned, replace entire BLDC motor. When replacing, confirm same manufacturer as inverter PCB (driver IC compatibility). Re-verify insulation resistance with 500V megger (≥1MΩ).
BLDC motor hall sensor failure → inverter miscontrol → overcurrent
Check: Check hall sensor voltage: with 5V supply, verify each phase switches 0V↔5V during motor rotation. Irregular switching or fixed voltage indicates faulty hall sensor.
What to do: If hall sensor is faulty, replace motor (field repair of sensor alone is impractical). After replacement, re-verify inverter motor control signals are normal. Simultaneously inspect fan blade.
BLDC motor winding resistance at room temperature is typically 5–15Ω — 0Ω means short, ∞ means open. Recording it before replacement provides a baseline for the next inspection.
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