Have autozone or advance pull codes and see if the evap temp sensor code comes up. I have a 2007 and this is the most common issue on our fusions. It's a sensor that tells the compressor when to cycle on and off to prevent freezing up. Issue is, when this sensor pops, a signal is sent to your ecu telling it your compressor is froze up and to not turn on at all. If this is your issue, its not an expensive part but the dash has to come out to get to the part for replacing. I did not want to take my dash out nor pay for someone todo it for me. So, what I did is trick the circuit that goes to the ECU into thinking the compressor is ok. My air once again blows cold as should. Only down side is, the compressor will run every time my AC is on no matter what fan speed I use. So I can't run low fan spped for long periods (road trips etc) or I risk the chance of freezing my compressor up. I live in Orlando so running our AC on full blast isn't an issue at all. Turn your AC on then pop your hood and see if your AC compressor is engaging? If not, I would def have a look at the evap temp sensor.
smac