As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU FAULT LIGHT COMES ON WITH APU BATT OFF LIGHT INTERMITTENT, VARIABLE VOLTS ON THE APU BATTERY DISPLAY AND THE APU CHARGER INDICATION CYCLING ON AND OFF ERRATICALLY. FOUND APU GENERATOR GROUND WIRE LOOSE AT ATTACH POINT. APU CHARGER AND APU OPS CHECK GOOD AFTER REPAIR AND RE-ATTACHMENT OF APU GENERATOR GROUND WIRE.