What was found
SWEET BURNING ODOR IN FRONT CABIN OF ACFT, NO VISUAL SMOKE. FOUND ODOR TO BE COMING FROM DIRTY RECIRCULATION FAN FILTER. REMOVED FILTER FROM ACFT IAW AMM TASK 21-22-22-0000-801 AND OPERATED AIR CONDITION SYS, TO FULL COLD & FULL HOT SETTINGS ODOR DID NOT RETURN GROUND RAN ENGINES ALSO TO ABOVE TO MENTIONED ACFT SETTINGS AND ODOR DID NOT RETURN. REINSTALLED RECIRCULATION FAN FILTER IAW AMM TASK 21-22-22-480-801 AND PLACED RECIRC FAN ON DMI. DMI CLEARED BY REPLACING FAN FILTER.