If you notice the exhaust suction is extremely weak or the fan sounds unusually quiet, it strongly indicates obstructed airflow. A "quiet" fan does not necessarily mean it is operating normally; rather, it often means the fan is choked by soot buildup and stalling, unable to move air effectively.
¶ 1. Perform an Airflow Diagnostic (The "Hand Test")
Place your hand at the end of the exhaust duct.
- If airflow is weak or absent: The air path within the machine or the ducting system is obstructed.
- Possible Cause: Excessive exhaust resistance prevents the fan from generating the negative pressure required to evacuate smoke.
¶ 2. Preliminary Inspection
- Filter Pad Check: Inspect the two black filter pads at the rear of the module. If they are coated in sticky residue, they act as a solid barrier blocking the airflow.
- Filter Bypass Test: Temporarily remove the black filter pads and monitor the airflow. If suction returns, clean or replace the filter pads immediately.
If the two black filter pads are heavily saturated with dust and debris, refer to the Exhaust Fan Filter Cleaning Guide for proper maintenance.
¶ 3. Inspect the Fan Impeller (Soot Buildup)
Over time, sticky resin and carbon soot can coat the fan blades (the impeller), significantly reducing their rotational efficiency.
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Visual Inspection: Use a flashlight to examine the blades. If the blades appear "thick" or fuzzy with buildup, they can no longer effectively "bite" into the air to create suction.
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Deep Maintenance: Refer to the Deep Maintenance Guide: Exhaust Fan Module to thoroughly clean the internal turbine fan and restore factory-spec suction performance.