As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BURNING SMELL WHEN INSTR COOLING FAN RUNNING PULL C/B ODOR GOES AWAY. C/W NO GO ODI PREV 2172 PER AMDS W/C 2120-2367. VERIFIED INST COOLING FAN IS BAD CAUSING THE NOISE AND BURNING SMELL IN COCKPIT. APU INLET IS CLEAN. REMOVED AND REPLACED INST COOLING FAN REF AMM 21-50. OPS CKS GOOD. NO MORE NOISE OR BURNING SMELL. (LP5335382)