I beg to differ with the above answer:
http://www.yarisworld.com/forums/showthread.php?t=20395
Anyway, what lead to the overheating before the radiator fan died? The A/C has nothing to do with the radiator. It is possible that your freon has leaked out due to a leak in the A/C condenser.
I say, have a mechanic that you trust look at all the relays, fuses, and wires that lead to the radiator fan. This is the first that I've heard of this, and I've been a member on YarisWorld for 3 years now.