'03 Trailblazer blower fan

I have an '03 Chev Trailblazer, and the blower fan only works on the high setting. For a while it would come on after the engine has had time to warm up, but now it doesn’t work at any lower speeds. What I need to know is where to find the temperature sensor and speed resistor pack that control the slower speeds. I don’t like running it at high speed all the time since it gets a little too loud, and I have to turn up the radio to hear it.

With winter coming I am going to need to run it almost constantly.

The resistor pack is usually located in the ductwork very close to the blower motor.

Is that under the cover right behind the hood, and inside the ductwork itself? I’m guessing that is to keep it cool.