My cooling fan motor isn't turning on my 2004 Pontiac Sunfire. My car is running hot because of this. How can I change the motor myself without spending a tonne of money on a dealership.

Have you checked the ecm for trouble codes ? The fan runs all the time as a safety to try to prevent the engine from overheating.

The cooling fan is controlled by a temperature switch located on the radiator or on the engine. When the temperature of the coolant exceeds the switch temperature rating, the switch closes and energises a relay that switched a voltage to run the fan and it will continue to run until the coolant temperature drops back below the opening point of the switch. In your case, you may need to have the cooling fan replaced.

I would test the ECT ( electronic coolant temp sensor ) first.

will turn on with a/c engaged
also will turn on when pre determined temp hase been reach when a/c is off
check relays and fuses also for power at fan motor

What are you going by to say it's overheating , temp gauge ? Have you test to see what the actual temp. is > Hook - up a scan tool ,what's the PCM - engine computer seeing for engine temp. ? 223 degress the PCM should turn on the cooling fan . You could buy a Non-Contact Infrared Thermometer With Laser Targeting at harbor freight ! Radiator very hot ????? What is the right temp .
Non Contact Infrared Thermometer With Laser Targeting

Could be a bad temp gauge . Is the coolant surging inside the cooling system ? Does it have a radiator cap ? Have you replaced it ?

It's inside the computer.

Turn the AC on. If the fan still does not turn on then you may have a fan relay or computer issue.

Also if the engine does not get hot enough the fan will not turn on. You may have a defective temp sensor or thermostat

make sure you have radiator full of coolant
run the car to operating temperature
check the operation of the cooling fan
feel the upper radiator hose and the lower radiator hose. they both should be hot.
if one is cold then you may have a bad thermostat or restricted flow
if cooling fan does not come on when engine is hot then you have bad cooling fan switch, relay or motor.
good luck

Yes, it's probably the PCM. I had the same problem, and upon replacing the PCM it started working again. If your cooling sending unit is new, and so many parts of your fan assembly are new, it's probably not receiving the signal from the sending unit. Hope this helps.

most likely the cooling fan has a short in it. disconnect the connector on the fan. If it doesn't blow now its the fan motor. If it still blows you have a short from the fuse to the motor. What this means is the hot wire is touching bare metal somewhere

the fan may be bad but you can find the hot side of the plug and run a hot to the battery and see if the fan comes on. if it doesent you know you have a bad fan if it does you can run a wire to the fuse panel so that it comes on when the car does and shuts off when you shut the car off