No airflow traced to burnt fan motor, not simple blockage
Aircon case in Jurong West, Singapore: airflow traced to indoor fan motor burnt out — open circuit on winding test after targeted diagnosis checks.
Case details
What client reported
The customer said the unit turned on and showed all the usual lights, the outdoor unit was running, but no air was coming out of the indoor unit at all. They assumed the filter must be completely blocked and had already tried cleaning it themselves with no improvement.
What we found
We worked from the simplest possible causes outward before concluding the motor itself had failed
- Filter removed and inspected — clean, no restriction
- Blower wheel removed and checked — no significant dust accumulation, wheel was balanced and free to spin manually
- Motor capacitor measured — value within 5% of rated specification, capacitor not at fault
- Power confirmed at motor — motor did not respond. Winding test showed open circuit on one pair.
The indoor fan motor coil had burnt out. Power was reaching the motor but it produced nothing. The winding test confirmed the coil had failed. No external part was responsible.
What we did
The motor needs replacement. This is a part swap, not a unit replacement. A matched motor was sourced and fitted on a return visit. Airflow was tested at all fan speeds and confirmed normal.
Full airflow came back after the motor swap. The outdoor unit, gas circuit, and PCB were all unaffected. The unit cooled normally from that point.
Timeline
Day 1
Customer reported complete loss of airflow despite unit appearing to run
Day 1
Motor capacitor tested within spec, motor still did not spin when powered, winding resistance showed open circuit confirming motor failure
Day 1
Filter, blower, and capacitor ruled out — winding test confirmed motor burnt out, replacement recommended
What we learned
Buildup vs. motor failure — different symptoms, different fix.
- Buildup builds slowly over months. The motor strains, noise rises, airflow weakens bit by bit. It doesn't stop suddenly.
- Motor failure is usually sudden. Airflow is fine one day, gone the next. The blower wheel won't spin even when power is on.
- Always test the motor capacitor first. It's the cheapest part that can stop the motor from starting. A dead capacitor looks just like a burnt motor.
- If the capacitor is fine and the motor still won't spin, a winding test gives a clear answer. Open circuit means the motor coil has failed.
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