As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT 3040, DURING TAXI OUT HEARD AUDIBLE NOISE (SQUEAL) THEN SIGNIFICANT CARBON ODOR THAT DIMINISHED INTESITY BUT STILL FAINT. CORRECTIVE ACTION: INVESTIGATED CARBON ODOR IN COCKPIT FOUND AVIONIC VENT BLOWER WITH A SLIGHT RATTLE. AFTER DISASSEMBLY STONG BURNING SMELL INSIDE FAN. REPLACED AVIONICS VENT BLOWER FAN. (LP 5814170)