What does this mean? My a.c blows cold air but at the lowest fan speed. Even if I turn it up all the way, it still is stuck at the slowest speed. I checked the code and it flashed "21". Anyone know what it means? Thanks

 

This means that there is an open or short in the solar sensor circuit. Sounds to me like an electrical problem with your A/C system. Go to your local A/C repair place and get it diagnosed.