What was found
FLT DECK RATHER COOL, UNABLE TO ADD WARM AIR AT FULL WARM. TURNING TRIM AIR OFF COULD WARM FLT DECK. ACFT GROUNDED. CONFIRMED DEFECT. WITH TRIM AIR SWITCH SET TO "ON", FLIGHT DECK DUCT TEMP DROVE COLD IN ALL TEMP SETTINGS. ACCOMPLISHED T/S IAW FIM 21-61, TASK 861, FOUND FLIGHT DECK TEMP SENSOR DIRTY. CLEANED FLIGHT DECK TEMP SENSOR IAW MM 21-61-10-100-801. CLEANED TEMP SENSOR FILTER IAW MM 21-61-06-100-801 AND PERFORMED FLIGHT DECK CABIN TEMPERATURE CONTROL AND INDICATION OPS TEST IAW MM 21-61-00-700-807-002. OPS NORMAL.