What was found
AIR TURN BACK, EICAS MSG 02 "R GEN OFF" DISPLAYED, R GEN OFF LIGHT ILLUMINATED. GENERATOR SWITCH RESET DID NOT CORRECT CONDITION. APU WAS TRANSFERRED TO DMI N. 247 BY MAINT REPORT P4264038-X3. : "APU FAIL". PERFORMED BPCU BITE TEST IAW FIM PROCEDURE 24-20-00, PG 180K. ACCOMPLISHED BOTH ENGINES RUN UP, ALL ELECTRICAL PARAMETERS WERE NORMAL. RT ENGINE IDG IS CONSIDERED OPERATIVE. SERVICED APU OIL TANK AS REQUIRED IAW AMM 12-13-04 PAGE 301, ACCOMPLISHED ERASE BITE PROCEDURE IAW FIM 49-11-01, PAGE 401. CHECKED APU OPERATION. WORKING PROPERLY. (K)