I'm in agreement with others to pursue the Blower Motor Resistor first, and work your way to the issues behind the HVAC Control Module. With my 2007 Coupe, I took on the HVAC Control Module Loose Connection between Boards described by CL770. This fix can be somewhat tedious as it is important to keep the Control Module Flow Control ***** in the same position as removed so that alignment with the Receiver Shafts inside the Upper Console remains the same. And even after I did this repair, I still had to go back & replace the Blower Motor Resistor to restore full HVAC Fan Control. (Note: It was much easier for me to re-install the HVAC Control Module after I removed the HVAC Vents located right above in the Upper Console. Gave me some visual access for aligning the Flow Control Shafts on the HVAC Module with their respective Receiver Shafts located inside. FWIW)

I have not done the potentiometer repair that has been mentioned here, as it was discovered & posted by a Crossfire Owner after I had addressed the loose board connection, but it's only a matter of time. When you have the Upper Console apart & the HVAC Control Module out, I'd do both fixes. Do you really care which one actually takes care of the problem? NOT ME! I just would not want to go back into the Upper Console again.