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.