As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
TEMP CONTROLLERS ARE NOT VERY RESPONSIVE. AFT CONTROLLER FOR EXAMPLE COULD NOT COMMAND MORE THAN 18'C DUCT SUPPLY EVEN AT THE 3 O'CLOCK POSITION. GROUNDED - YES. REMOVED AND REPLACED TRIM AIR PRESSURE AND SHUTOFF VALVE REF B737-800 AMM 21-62-01/401. OPS CHECK GOOD, GROUND VERIFICATION SUCCESSFUL. FOUND OLD VALVE IN MANUAL MODE, SUSPECT TO BE AT FAULT.