As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE PARKED ON THE RAMP ,COCKPIT BEGAN TO FILL WITH SMOKE WHICH SMELLED OF OIL. SMOKE CLEARED WHEN BLEED AIR TO COCKPIT PAC WAS SHUT OFF. LOW AIR VOLUME FROM OVERHEAD VENTS HAD BEEN NOTED.REMOVED DEFECTIVE COCKPIT ACM AND REPLACED WITH OVERHAULED UNIT IAW M/M CH 21-51-00. OPERATIONAL CHECK GOOD.