As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FWD CABIN TEMP CONTROLLER REQUIRES MUCH HIGHER POSITION TO MAINTAIN NORMAL TEMP - SOMEWHAT ERRATIC. ACFT GROUNDED. BITE CKD BOTH ZONE CONTROLLERS REF FIM 21-62, TASK 801, NO FAULTS LOGGED. FOUND FWD ZONE FILTER CLOGGED. CLEANED FILTER AND OPS CHECKED REF AMM 21-61-06. ALL GROUND FUNCTIONAL TESTS PASS.