Narrative:

This aircraft had the #2 engine generator deferred. We had diverted that morning into ZZZ1 when the APU repeatedly automatically shut down in-flight. While maintenance worked on it; we went to the hotel to rest. That evening; we came on duty again to ferry the aircraft to ZZZ2 with the #2 engine generator still deferred. Climbing and approaching our filed cruise altitude of FL320; the APU automatically shut down; leaving us with a single main electrical power source in IMC at night. Given the history of the APU automatic shutdowns earlier that day and the night IMC WX with thunderstorms in the area; we declared an emergency with ATC for an immediate return to ZZZ1. Cfds again indicated multiple problems with the APU. The 2 mechanics aboard agreed with our assessment that the APU was not reliable despite their efforts; and that we had only 1 reliable generator on the aircraft. The diversion was coordination with operations; dispatch; and maintenance. After blocking in at ZZZ1; the first officer and I stayed with the aircraft and the mechanics to attempt a repair of the #2 engine generator. Multiple other mechanical problems developed with the airplane; and after sunrise we all left to the hotel. By the evening the repair attempts were still unsuccessful.

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Original NASA ASRS Text

Title: AN A320 WITH AN ENG GENERATOR MEL'ED EXPERIENCED AN APU AUTOMATIC SHUTDOWN AND RETURNED TO THE DEP STATION. EMER DECLARED.

Narrative: THIS ACFT HAD THE #2 ENG GENERATOR DEFERRED. WE HAD DIVERTED THAT MORNING INTO ZZZ1 WHEN THE APU REPEATEDLY AUTOMATICALLY SHUT DOWN INFLT. WHILE MAINT WORKED ON IT; WE WENT TO THE HOTEL TO REST. THAT EVENING; WE CAME ON DUTY AGAIN TO FERRY THE ACFT TO ZZZ2 WITH THE #2 ENG GENERATOR STILL DEFERRED. CLBING AND APCHING OUR FILED CRUISE ALT OF FL320; THE APU AUTOMATICALLY SHUT DOWN; LEAVING US WITH A SINGLE MAIN ELECTRICAL PWR SOURCE IN IMC AT NIGHT. GIVEN THE HISTORY OF THE APU AUTOMATIC SHUTDOWNS EARLIER THAT DAY AND THE NIGHT IMC WX WITH TSTMS IN THE AREA; WE DECLARED AN EMER WITH ATC FOR AN IMMEDIATE RETURN TO ZZZ1. CFDS AGAIN INDICATED MULTIPLE PROBS WITH THE APU. THE 2 MECHS ABOARD AGREED WITH OUR ASSESSMENT THAT THE APU WAS NOT RELIABLE DESPITE THEIR EFFORTS; AND THAT WE HAD ONLY 1 RELIABLE GENERATOR ON THE ACFT. THE DIVERSION WAS COORD WITH OPS; DISPATCH; AND MAINT. AFTER BLOCKING IN AT ZZZ1; THE FO AND I STAYED WITH THE ACFT AND THE MECHS TO ATTEMPT A REPAIR OF THE #2 ENG GENERATOR. MULTIPLE OTHER MECHANICAL PROBS DEVELOPED WITH THE AIRPLANE; AND AFTER SUNRISE WE ALL LEFT TO THE HOTEL. BY THE EVENING THE REPAIR ATTEMPTS WERE STILL UNSUCCESSFUL.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.