Our experience has found that moisture was causing corrosion leading to the failure of the Bendix GCU.
Although Service Bulletin SBF2-12-001 is not mandatory, API strongly recommends compliance during the next maintenance event in which the ailerons are removed from the aircraft.
If you have the centrifugal compressor impeller with the designated part and serial number, accomplish the initial borescope inspection at the next designated airframe inspection.