Post #1
The HVAC blower fan 5-speed control on my vehicle went to a 3 speed and eventually to OFF or high speed only. Did a little research and narrowed it to be the motor resister control module. Picked up an after market on ebay for 15 bucks shipped ($109 dealer part). Watched a video on youtube and changed it in 20-min tops. 2 (5.5 mm) screws and 2 clips. The old one had rusted and was literally falling apart (surprising high speed worked). If your fan speed control isn't working, don't spend your hard earned cash on a simple fix. Youtube and ebay can save you money to buy more jig heads...lol.

Post #2
Here are the pictures from the old HVAC Blower Motor Resistor Control Module




Recently I had been seeing vapors coming through the vents when the hvac system goes from ice cold AC to just running the vent with the ac off. So there has to be moisture internally. This part is located in the lower portion of vent duct system. It goes to reason that some of the moisture is collecting here and causing the corrosion. The rectangle base of the part is just plastic. Wonder if drilling a vent hole for air circulation would help? or just let it go since this part limped along for 8+ years....

Hope this helps