Cassette Airflow Weakening: Corroded Motor Contacts, Not Blockage
Aircon case in Hougang, Singapore: airflow traced to corrosion at motor contact points reduced fan voltage, not a blockage issue after targeted diagnosis checks.
Case Details
| Unit | DaikinCassette |
|---|---|
| Age | 10 years old |
| Location | HDBHougang, Singapore |
| Reported | Airflow from the ceiling unit noticeably weaker over the past few weeks. Filter had been cleaned but it made no difference. Unit still producing cold air, just very little of it. |
What We Checked
- Filter was clean — confirmed not the cause.
- Motor voltage under load was 15% below specification.
- Visible corrosion at the motor terminal connection points on the PCB.
The Diagnosis
The west-facing location of the unit meant salt air exposure over the years. Corrosion at the motor contact points had built up, creating resistance in the voltage path to the motor. The motor was receiving less power than it needed to run at full speed, so the fan slowed down even though the unit was trying to run it at full.
What Fixed It
The motor itself is fine — the corroded connection is the problem. Cleaning the contact points, applying a protective coating, and confirming voltage returns to spec will restore the airflow without any motor replacement.
After the corroded contacts were cleaned and protected, motor voltage returned to normal and airflow strength came back to pre-corrosion levels. The unit has been running at full capacity since.
Why This Happens
Weak airflow is not always a blocked path.
- A cassette with a clean filter that still pushes weak air often has a voltage drop at the motor, not a blockage downstream.
- Corroded contact points at the motor reduce the voltage it receives, slowing the fan even when the filter is clear.
- Testing motor voltage under load is the fastest way to rule out a blockage and find the actual cause.
Related Reading
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