Thats exactly what it is. I have the same setup and i had my grille block off while modifying it. The resulting increased airflow had the fan going like a wind turbine. The power fed back into the system is virtually nothing but the led was fully on which was took a bit of getting used to. Just shows how much cooling engines get: too much! I now have an opening of about 3" by 14" and the led only comes on when the fan comes on.
ollie
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