What you described sounds like the blower motor resistor has failed. When they fail, oftentimes the blower motor will only work in the high-speed position. If I understand correctly, that is what is happening for you.
Also, the idea that you hear the compressor engaged tells me the controller/switch is working.
Based on what is happening, I would replace the blower motor resistor. It is located under the dash on the passenger side and is mounted to the HVAC box. See pic 1 below.
The remaining pics are the directions for replacing the resistor.
Let me know if this helps or if you have other questions.
See pics below.
Images (Click to enlarge)
Monday, January 23rd, 2023 AT 6:51 PM