As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
NR 4 WINDOW HEAT CONTROL UNIT (RT FWD) ON E4 2 RACK HAS FLASHING "WHCU LRU" LIGHT AND WILL NOT RESPOND TO BITE COMMANDS. ACCOMPLISHED T/S PER FIM 30 41 00 810 801 AND FIM 30 41 00 810 807. REPLACED NR 4 WINDOW HEAT CONTROL UNIT (M323) PER MM 30 41 11 000 801 / MM 30 41 11 400 801. PERFORMED WHCU INSTALLATION TEST PER MM 30 41 11 400 801 AND OPERATIONAL TEST OF WINDOW HEAT SYSTEM PER MM 30 41 00 710 801, ALL TESTS PASS.