What was found
PHX - EMERGENCY LANDING - FLT 0272 - ON SHORT AND FINAL INTO PHX EN ROUTE FROM SNA ENCOUNTERED SMOKE AND A STRONG ELECTRICAL BURNING ODOR IN CABIN, DONNED MASKS AND DECLARED EMERGENCY. MAINTENANCE FOUND THE AVIONICS COOLING FAN (EXTRACT FAN) BEARINGS SEIZED CAUSING FAN TO OVERHEAT. REMOVED AND REPLACED AVIONICS COOLING FAN IAW AMM 21-26-51-000-001; OPERATIONAL CHECK WAS GOOD. *S/D* VENDOR CONFIRMED FAILURE OF AVIONICS COOLING FAN S/N 1204; UNIT WAS SEIZED. FRONT BEARING FAILED CAUSING IMPELLER TO BIND AGAINST BELLMOUTH. REPLACED FRONT & REAR BEARINGS, FRONT FLANGE, CENTER HOLE, AND BEARING FACE, BALANCED ROTOR AND MOTOR/IMPELLER, FUNCTIONAL TESTED UNIT IAW CMM 21-26-42.