What was found
STL - FLT 163 - EN ROUTE PHL-PHX - WHILE IN CRUISE AT FL350, A VIBRATION WAS FELT IN THE COCKPIT AREA, FOLLOWED LATER BY AN ELECTRICAL ODOR. WHEN THE ODOR BECAME PRESENT, THE CREW PUT ON THEIR OXYGEN MASKS AND THE FLIGHT DIVERTED TO STL, AND LANDED WITHOUT INCIDENT. MAINTENANCE REPLACED THE AVIONICS FAN. OPS CHECKED NORMAL. (M)