Assuming you're talking about the blower motor, because the blower motor resistor is faulty, and needs to be replaced. On the high setting, it doesn't go through the resistor - on the other settings, it does.
your fan resister is bad,it should be located under glove box, on heater box!! under dash.
If it has only high speed, the blower motor resistor has to be replaced to get all speeds back.
You will have only cold air coming thru your heater ducts if your core is defective.
DEFINATLY NOT! a transmission for a 2.4 was designed for a 2.4 ONLY! not only will it not fit, it will not be able to handle the power the 3.1 throws
Blower fan inoperative or only works on high speed.
The heater motor speed resister is burned out.
Defective Blower Motor Resistor Pack.
you may not have the heater water hoses plugged in
you have a bare wire touching on your blower motor
it is a heater. heat. it blows heat. warm air
Defective heater resistor pack.