As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
RETURNED TO THE FIELD WHEN THE LT GENERATOR WENT OFF LINE AND THE APU WOULD NOT START. APU START SWITCH AND APU ELECTRONIC CONTROL UNIT WERE REPLACED PREVIOUSLY DUE TO APU ALTITUDE STARTING PROBLEMS. THE ECU TESTED WITHIN LIMITS. APU START SWITCH WAS NOT ROUTED BACK TO HOME SHOP. THE APU DID NOT EXPERIENCE ANY OTHER EVENTS.