As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMB THE FLIGHT DECK BECAME HOTTER THAN NORMAL. WE COULD NOT GET IT UNDER CONTROL VIA NORMAL MEANS. SO WE FOLLOWED THE QRH. ONCE THE TRIM AIR WAS TURNED OFF WE REGAINED CONTROL OF THE TEMPERATURE. WE LEFT THE TRIM AIR OFF FOR THE REST OF THE FLIGHT. GROUNDED - YES. REMOVED AND REPLACED TRIM AIR MODULATING VALVE FOR THE CONTROL CABIN DUE TO MULTIPLE HISTORY TEMP CONTROL CABIN WITH TRIM AIR REF B737-900 AMM 21-61-21.