my 2008 chevy cobalt ac wont come on, checked the fuses , wires, senor, resistor, relay,switch , and blower motor fan still will not work.

Have you checked the compressor clutch to ensure it's engaging. If not you might need to replace your compressor.

The compressor engages... Could fuse box have something to do with it? When test relay the from part of relay is got but no power on back part. Front meaning side of relay towards motor back meaning towards outside. Nothing else in fuse box seems affected