What was found
AIRCRAFT RETURNED, LT GENERATOR FAILURE, APU DID NOT START AT 35 000 FT, 24 22 25 EICAS MESSAGES, 01 GEN OFF DISPLAYED AND 01 AS BUSS OFF REMAINED ILLUMINATED. QRH ABNORMAL PROCEDURE WAS PERFORMED, PAGE 09-03, RETURNING. DURING TEST WAS DETECTED LOW QUANTITY OF OIL AND LEAK IN THE IDG, IT WAS REPLACED. LATER, AIRCRAFT RETURNED, AGAIN 24 11 03 EICAS MESSAGES, 01 GEN DRIVE DISPLAYED AND GEN DRIVE LIGHT ILLUMINATED. QRH ABNORMAL PROCEDURE WAS PERFORMED PAGE 09-04, RETURNING. THE APU WAS TIRED TO START SEVERAL TIMES AND IT STARTED AT 20 000 FT. DURING OVERNIGHT SERVICE, THE LT IDG WAS REPLACED IAW MM 24-11-01 AND SENSORS MODULE WAS REPLACED IAW MM 49-53-08, TESTED CORRECT.