When you say it would not cool are you saying the compressor would not start/run while the selector switch was in the high cool position or that the air coming out of the unit didn't feel cool to your hand? On low cool when the compressor is running my discharge air temp is lower than when running on high cool with the compressor running. This is due to the air's ability to give up more heat when traveling across the evaporator coils at a lower velocity.
2006 23B Hybrid with 10k round bar WDH
2011 F150 4x4 SCREW Ecoboost, Max Tow, Integrated TBC, 3.73 LS axle, Firestone Ride Rite airbags.