I have an 12 model C2. The blower motor in the dash is blowing slowly out of the vents. I checked cabin filter and it was somewhat dirty not to terribly bad. As soon as I removed the fan blows really hard in the dash, but still no change in blower speed at vents. It doesn't matter the position of mode switch it stays the same speed. Blend Door works like it should as well. Is there something I'm missing??
There are two blend doors one for temp and one for airflow direction. temp is mounted by cabin filter and the direction door is up top left corner. Do you get a ratcheting noise when you first key on the unit? Door control servos go bad often just several plastic gears inside.
pop the back off of fan and you'll find green in the circuit board from your story the blend door is working and the temp. door the fan is just not changing speeds if this is correct then it should be a fan it is in default (like an old ford and the fan will work on high only)
OEM trained in wiring and all engine platforms for over 20 years