As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IN DESCENT SMOKE APPEARED IN COCKPIT AND CABIN. TURNED OFF ANTI-ICE SWITCHES AND SMOKE DISAPPEARED. FOUND OIL RESIDUE IN DUCTS APPARENTLY CAUSED BY APU OIL BEING OVERSERVICED. CHANGED ANTI-ICE PRESSURE REGULATING VALVE WHICH APPARENTLY FAILED AND SMOKE TO APPEAR. CHECK-C 12-14-99 STL.