First guess would be a bad ignition switch.
Blown fuse, defective blower motor, or defective blower motor resistor pack.
You will need to locate a few wires that are located on a small plate between the heater and air system of a 2002 Kia Sportage. The resister pack rests there and can be removed and replaced to fix the blower.
Check the fuse and relay first. Then check the blower resister, then the blower motor itself. One of these is probably the cause of the failure.
you access the fan blower by removing the windshield wiper motor from the outside of the car.
Look under the dash on the passenger side
I have a Saab 9-5 and its blower motor is located in the front of the windshield underneath the wipers
Under the glove box on the passenger side. Black round thing.
If the front blower and the front windshield wiper do not work on a 2004 Chevy Trailblazer, it could be the fault of the relay switches on the blower and the wiper. Also check the fuse box on top of the battery for a multi-function fuse that might be blown.
It is located behind the coolant and windshield washer reservoirs. The two wires on the blower motor will lead you to it.
Your blower motor is getting ready to fail, it is usually gradual. I have replaced 2 on my 200 Kia Sportage and in both cases the low sppeds failed first. This may also require the relay be replaced as when it finally fails it can take the relay out.
The blower motor resistor is located under the hood, in the right hand cowl, behind the windshield washer bottle.............
just take out 3 screws from the fan and unplug it. take blower out of housing and replace, should only take about 20 minutes.