[floresmaxima]

I have a 97 Toyota Corolla and the problem I'm having is that my radiator fan is not working (I think)the reason I notice this is becuase I was getting a mix between heat and cold. I'll get heat and all of a sudden cold air will come in so what I did was replaced the thermostat and put everything back together and let the car run for about half an hour and found out the radiator fan was not working at all, but I started getting heat constantly without any problem. Next thing I did was run a wire from the battery directly into the the radiator fan and the fan works, so I know I'm good there. The next thing I did was replace the sensor the one on the water neck (coolant fan sensor) I believe that's what is call and still the radiator fan does not come on at all so now I don't know what other steps I should take in order to fix this problem,but I should mention that when I put my ac and put on heat the fan starts to work so don't know if this is suppost to happen. Now any idea of what the problem could be or where should I be looking since I already replace the thermostat and the coolant fan swicht sensor the one by the water neck thank you.