Is the fan motor going to need replacing?

Not in most cases like this. Gradual airflow loss usually comes from buildup, not a failing motor. A chemical overhaul clears the restriction and the motor continues running normally.

Will this keep happening even after cleaning?

A chemical overhaul removes the deep buildup that filter washing misses. After cleaning, regular servicing every 3 to 4 months slows regrowth significantly.

Do I need to replace any parts for this?

No parts are needed in most buildup cases. The restriction is cleared by cleaning, not by replacing components.

Cold air but weak throw traced to blocked airflow path

Aircon case in Bishan, Singapore: airflow traced to heavy dust and lint buildup on fan barrel and evaporator coil after targeted diagnosis checks.

Case details

What client reported

The air coming out is cold, but it feels like less and less each week. The fan is still spinning — I can see it through the louvre.

ProblemAirflow

UnitMitsubishi Electric · Wall-mounted · 4 years old

LocationHDB · Bishan, Singapore

What we found

Weak airflow with a spinning fan rarely means motor failure. Motors tend to fail completely, not gradually. We checked for blockages first.

Fan blades coated in thick dust and lint despite a recently cleaned filter
Dust buildup on the evaporator coil and fan barrel behind the filter
Motor behaviour looked normal during operation
No signs of bearing drag during manual rotation

The filter catches most dust, but fine particles still get through. Over time they build up on the coil fins and fan blades. This adds weight to the fan and restricts airflow. The motor was working normally — the system was clogged. Cleaning the filter alone doesn't remove this deep buildup.

What we did

No motor replacement is needed. A chemical overhaul — disassembling the indoor unit and removing buildup from the fan barrel and evaporator coil — should restore full airflow. If airflow is still weak after cleaning, we can test the motor then.

We removed heavy buildup from the fan barrel and coil fins. After reassembly and test run, airflow returned to normal strength. The original motor is still running fine.

Timeline

Day 1

Airflow noticed getting gradually weaker each week

Day 4

Manual rotation check of motor and direct inspection of fan barrel before any parts diagnosis

Day 4

Chemical overhaul completed — airflow restored to normal

What we learned

How to tell motor failure from blocked airflow.

A failing motor usually stops suddenly or makes grinding noises — gradual airflow loss over weeks points to buildup, not the motor.
Buildup settles on the fan barrel and coil fins over time, adding weight and restricting the air path even when the motor spins normally.
Cleaning the filter only reaches the surface. Deep buildup inside the unit needs a chemical overhaul to fully clear the restriction.

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