As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CABIN PAC OVERHEAT WHILE USING AIR CONDITIONING FROM THE APU ON THE GROUND. SMOKE FILLED THE CABIN, APU AND PAC WAS SHUT DOWN DURING FLIGHT FROM IAD TO ADS. INSPECTION OF ACM REVEALED BLACK OIL IN SIGHT GAUGE. REMOVED FORWARD ACM AND INSTALLED CUSTOMER SUPPLIED OVERHAULED UNIT AND SERVICED WITH OIL. CHANGED COALESCER SOCK AND PERFORMED OPERATIONAL TEST. NO DISCRIPTION NOTED AT THIS TIME. REF CESSNA 750 MM 21-51-00.