As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PLEASE CHECK FOR WELS FAULT M3351WG04 WCU CLASS26 LOCATED UNDER SEAT 39D REFER HAECO NON-ROUTINE NO.9478972, PERFORMED THE TROUBLE SHOOTING AND WIRI. NG CHECK FOUND THE WCU FAILED REPLACED THE WCU AND CARRIED OUT I NSTALLATION TEST THE TEST RESULT FOUND NORMAL AS PER AMM 33-51-0 7-01A-520/720A-A REV.181 FIM 33-50-F1-E7A-421A-A REV.162