What was found
UPON LEVEL OFF AT FL320, CREW REPORTED A LOUD RUMBLING & VIBRATION HEARD BEHIND OR UNDER CAPTAIN'S SEAT. THIS WAS FOLLOWED BY AN ACIDIC ELEC SMELL. CREW DONNED O2 MASKS & TURNED COMMERCIAL, GALLEY & CAB BUTTONS OFF. SMELL QUICKLY DISSIPATED, COMMERCIAL TURNED BACK ON. ACCOMPLISHED CABIN AIR QUALITY JOB CARD 26L00021001. FOUND AVIONICS BLOWER FAN AS CAUSE OF RUMBLING, VIBRATION & BURNING SMELL. R & R 20HQ BLOWER FAN IAW AMM 21-26-51-000-001-A, ALL PARAMETERS NORMAL.