^ right

Go to a shop with a proper recovery system to measure your refrigerant levels.

The Aux fan will affect idle performance noticably (see other thread about this), but if it's bad in all conditions, it could be a bad part in any section of the A/C loop. Check obvious first (condenser), and move inwards (to evap).

At this point, it may be beneficial to go to a shop who can help diagnose A/C performance.