As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER LANDING APU STARTED NORMALLY BUT APU GEN SHOWED NO VOLTS, NO FREQ'S WITH BLUE APU OFF, BUS LIGHT ILLUMINATED. ALL C/B'S CHECKED IN. APU GENERATOR WOULD NOT SWITCH ON & TAKE POWER. ACFT ACCEPTED GROUND POWER OK. ACFT GROUNDED. ACCOMPLISHED APU OPS TEST IAW AMM 49-11-00-710-801. OPS TEST GOOD. APU GEN SWITCHED ON, TOOK LOAD & OPERATED NORMALLY. NO FURTHER DEFECTS NOTED.