What was found
R1 WINDOW OVERHEAT ILLUMINATED AFTER START. RAN QRH PROCEDURES. IT EXTINGUISHED. DURING FLIGHT IT OVERHEATED AGAIN. WE RAN THE SAME PROCEDURES AND IT AGAIN EXTINGUISHED. GROUNDED - YES. VERBAL FROM CREW THE OVERHEAT HAPPENED 3 TIMES (SIG) COULD NOT DUPLICATE THE OVERHEAT CONDITION HOWEVER, R1 WINDOW ONLY HEATS TO 84 DEGREES. TRIED SPARE SENSOR BUT R1 WINDOW THROWS AN OVERHEAT LIGHT IMMEDIATELY AFTER TURNING ON. WHCU FAULT HISTORY SHOWS SEVERAL SENSOR FAULTS. TRIED NEW WHCU, NO HELP. REINSTALLED ORIGINAL WHCU. (SIG) REMOVED R1 WINDOW REF B737-900 AMM 56-11-11-000-801. INSTALLED NEW R1 WINDSHIELD REF AMM 56-11-11-400-801. WINDOW AIR OUTLET VALVE TEST COMPLETED PER AMM 56-11-710 WINDOW SYSTEM TEST COMPLETED PER AMM 30-41-00.