As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
A/C PACK LIGHT ILLUMINATED ON MASTER CAUTION RECALL ON DESCENT INTO SEATTLE. INITIALLY RESET THEN ILLUMINATED RAN QRH WOULD NOT RESET. FOLLOWED PROCEDURE PACK LIGHT STAYED ILLUMINATED FOLLOWING QRH TURNED PACK OFF LIGHT EXTINGUISHED. GROUNDED - YES. REF B737-900 FIM 21-53 TASK 821, B737-900 AMM 21-61-20-400-801. COULD NOT DUPLICATE. AS A PRECAUTION DUE TO HISTORY, REMOVED AND REPLACED NR 1 PACK/ZONE TEMP CONTROLLER. OPS TESTS NORMAL.