Why the fan barrel matters
The fan barrel rotates whenever the indoor unit moves air. Dust and residue on its blades can change how the surface looks and may contribute to uneven or reduced airflow.
Why the filter does not clean it
Removing and washing the filter does not physically contact the fan barrel. Inspecting and cleaning it requires controlled access, protection of surrounding surfaces and care around electrical components.
What a professional process should include
A deep clean should explain which accessible components are being cleaned, contain the wash water and finish with a system check and test run.
The practical takeaway
The fan barrel is one reason a filter-only clean and an internal deep clean are not the same service.