What was found
LEFT FORWARD WINDOW OVERHEAT LIGHT WILL NOT EXTINGUISH, TRIED TURNING OFF FOR 5 MINUTES AND THEN BACK ON LIGHT COMES ON INSTANTLY WHEN TURNING SWITCH BACK ON. GROUNDED - YES. PLACED WHCU IN OVERRIDE MODE - NO HELP, BOX WAS LOGGING P5-9 FAULT. SWAPPED WHCU - NO HELP, SWAPPED BACK. AFTER SEVERAL MINUTES SYS STARTED OPERATING NML. CKD WINDOW HEAT FILM AND SENSOR RESISTANCE PER B737-9 AMM 30-41-21, BOTH CKD NML. REPLACED P5-9, INSTL. TEST AND SYSTEM TEST NORMAL B737-9 AMM 30-00-02.