Toyota Repair: Toyota corolla hot engine, radiator hoses, coolant leak

Question
Toyota corolla (1990 model, manual transmission). A week back, I changed the radiator aux fan as it was already stuck up. There after, I noticed that the engine temp goes hotter than normal and the aux fan does not kick in unless I turn on the aircon unit.  The engine coolant boils but I can't see any coolant leak in the radiator, hoses or water pump.  A friend says that maybe I have to replace the switch of the radiator aux fan as it may have been damaged when the original aux fan got stuck up.  Is he right?  

Answer
The aux fan is only supposed to come on when the A/C is turned on, there is another cooling fan that is the main cooling fan which should turn on as the engine comes to operating temperature, is it working?  If it never turns on look for the temperature control switch on the bottom of the radiator, with the key in the on position disconnect the electrical connector and the cooling fan should run, if so replace the temp switch.