BUS WAS IN SERVICE AND ON ROUTE WITH STUDENTS ON BOARD. BUS INTERIOR STARTED FILLING WITH SMOKE. DRIVER PULLED OVER AND DID AN EMERGENCY EVACUATION OF STUDENTS. SUBSEQUENT INVESTIGATION REVEALED THE A/C 24 VOLT ALT HAD FULL FIELDED AND CAUSED THE WIRING TO COMPLETELY MELT THE SHEATHING ON THE ALT POWER WIRE. BACKFEED THROUGH THE SYSTEM CAUSED THE CONTROLLER TO BURN UP INSIDE THE BUS. CARRIER HAS TOLD US THEY KNOW OF THIS PROBLEM AND THEY HAVE A FIX FOR IT. THIS IS ONE OF AT LEAST 10 WE HAVE HAD HAPPEN. SOMETIME IT BURNS UP THE CONDENSER MOTORS AND THE EVAP MOTORS AS WELL. *TR