As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON THE GROUND WITH THE APU RUNNING FOR SEVERAL MINUTES, SECONDS AFTER SWITCHING BLEED AIR ON, SMOKE STARTED COMING INTO THE CABIN FROM ALL WEMACS VENTS. REPLACED APU IAW 560XL MM CH 49-10-00 SERVICED OIL RAN LK AND OPS CK GOOD. OLD APU SERIAL P-638 TSN HOURS 615.2 AND CSN 1125, NEW APU SERIAL P-324 TSN HOURS 3044.9 CSN 4801. UNIT REPAIRED IAW 560XL MM 49-10-00. APU WITH 2380 ENGINE OIL