What was found
AT 10000 ON CLIMBOUT NOTICED ARCHING OF WINDSHIELD HEAT VENT ON CAPTAINS FWD WINDOW. FOLLOWED BY WINDSHIELD CRACKING. GROUNDED - YES. AIR TURNBACK -- REMOVED L1 WINDOW PER B737-900 AMM REF 56-11-11-000-801 REPOSITIONED WINDOW HEAT TAP ON TB5010 FROM POS 2 TO POS 1 FOR INSTALLATION OF AN H13 WINDOW. REF B737-900 WDM 30-41-11-2 PG. 2. INSTALLED L1 WINDOW PER AMM REF 56-11-11-000-801 THROUGH PG. 14 STEP (6). WINDSHIELD WIPER ARM AND BLADE INSTALLATION COMPLETED PER AMM 30-42-31-000-801 & 30-42-11-400-801. OPS CK GOOD. COMPLETED INSTALLATION OF L1 WINDOW PER AMM REF 56-11-11-000-801.