The design of this cooling system is bad. I too upgraded to the “Pro” unit that has two solar cells. The cells developed a “crust” after two summers in the sun, as if the factory failed to remove the protective film from the cells during assembly. I was unable to remove this “crust”.

It would be helpful, if you could provide details of the replacement cell you used. I also replaced the motor with a Mabuchi, but the noise continues, when the unit is in place with the shaft facing downward.