This weekend I went on a trip with my Mustang, and it was super hot, so I had to run the Ac at full blast to get it to cool down. I noticed the fan would spin at max, then after a few minutes it would almost stop and kinda sputter. I turned the system off and back on, and it still doesn't work. Then I try it again a half hour later and it does the same thing. Runs like normal then sputters. Could this be a fuse? Or what else could it be?

 

You could be low on charge or your expansion valve is freezing up from a weak compresson (and needs to thaw before it works again). Do not go out and just throw refrigerant into your system. Overcharging can damage the system or, if you have a leak, it will work for a short while and then have issues after a short while.

Get some A/C manifold gauges and see what the Hi/Low side readings are with the system running. It will help you pinpoint the issue. If you don't know how to read the gauges, pay a shop their $60-$75 check up fee and they'll tell you what's up. Or, learn how to read them...