I suspect that the wiring harness to the Radiator Fan got disturbed inadvertently during the Alternator replacement.
This could include a connector plug being pulled loose, a wire cut or broken or "pinched" and thus in contact [grounded] with/to a component of the engine which is grounded.
you have to remove the radiator and the a/c condenser to pull alternator also cooling fans
you have to remove the radiator and fans and all the covers and then the alternator will be a piece of cake to pull out and replace
Front left of engine. Behind radiator and fans, halfway down
Bad thermostat, fans not working or coming on when they are supposed to, bad waterpump, bad radiator or radiator cap.
a bad termastat
Low coolant? Radiator dirty or plugged? Bad thermostat? Bad water pump? Cooling fans not working? Bad radiator cap?
More than likely the radiator fan resistor has gone bad. It is located at the bottom corner of the radiator.
Low coolant cooling fans not working thermostat not opening radiator dirty or plugged water pump not working system "airbound" defective radiator cap hoses collapsing
BAd thermostat. clogged radiator, cooling fans not working, blown head gasket.
TAke it to the garage. You have problems that need to be looked at. WELL I HAD THE SAME PROBLEM WITH MY CAR SAME EXACT THING........ THE LEAKING WAS THE RADIATOR, THE RADIATOR SIDE COVER WAS LEAKING SO I HAD TO REPLACE THE RADIATOR THATS ONE THING FIX, THE OTHER WAS THE FANS THE MAIN FAN WAS NOT WORKING SO YOU HAVE TO REPLACE THE WHOLE RADIATOR FANS .... AND THAT WOULD SOLVE YOUR PROBLEM WITH THE OVERHEATING AFTER THAT MAKESURE YOUR WATER PUMP IS GOOD MAKE SURE AFTER ALL THAT REPAIRS CHECK FOR LEAKS UNDERNEATH THE TIMING COVER IF YOU SEE LEAKS , THEN YOUR WATER PUMP WENT OUT THEN THAT WOULD BE ANOTHER BIG PROBLEM
You could have a stuck thermostat or your cooling fans aren't working.
Low coolant? Cooling fans not working? Water pump not circulating coolant? Radiator plugged or restricted?