As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) DURING FLIGHT, A WARNING NOTIFICATION WAS GIVEN TO THE PILOT ON THE GDU DISPLAY STATING FAN FAULT. UPON INSPECTION AT THE MAINTENANCE FACILITY, WE FOUND THAT THE FAN WAS STRUGGLING TO SPIN FOR COOLING. WORRIED THAT THE FAN WILL CAUSE THE GDU TO OVERHEAT, WE DECIDED TO CHANGE IT. SENT THE ITEM TO AN AVIONICS SHOP AND IT WAS REPAIRED WITH A NEW FAN. NO OCCURRENCE HAS HAPPENED SINCE THEN.