As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ACRID ODOR WITH THE RECIRCULATION FAN ON. NO ODOR WITH THE FAN OFF. REPLACED RECIRCULATION FAN IAW AMM TASKS 21-22-16-000-801 AND 21-22-16-400-801. LEAK & OPS CHECKED GOOD. RAN AC SYS WITH RECIRCULATION FAN ON - NO NOTICABLE ODOR NOTED. RETURNED TO SERVICE.