What was found
FLT 0625 - ON TAXI OUT AT PHX THE COCKPIT FILLED WITH A STRONG ELECTRICAL BURNING ODOR, TURNED OFF AIR CONDITIONING PACKS, RECIRCULATION FAN, ENGINE GENERATORS, AND BURNING ODOR DISSIPATED. AIRCRAFT RETURNED TO GATE. MAINTENANCE DISCOVERED THE RECIRCULATION FAN CIRCUIT BREAKER EXTENDED, REMOVED AND REPLACED THE RECIRCULATION FAN IAW BMM 21-21-22-401; OPERATIONAL TEST OF FAN WAS GOOD.