As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LEFT PACK LIGHT ILLUMINATED AT CRUISE. QRH PROCEDURE COMPLETED AND UPON TRIP RESET THE LIGHT EXTINGUISHED. SHORTLY AFTERWARDS ON MASTER CAUTION RECALL, THE PACK LIGHT ILLUMINATED BUT EXTINGUISHED UPON MASTER CAUTION RESET. REILLUMINATED AT CRUISE AND PACK LIGHT STAYS ON NOW. GROUNDED-YES. REMOVED AND REPLACED RAM AIR EXHAUST ACTUATOR ON THE LEFT SIDE, REF B737-900 AMM 21-51-27-400-801.