We have an outside ac unit... we came home in the evening and noticed the house was warm.. the outside 30A fuse was blown... we replaced them and the unit cooled for about 30 hours.. came home this evening and it is not working again... blown fuse... could it be the compressor or the capacitor? The unit is approximately 8 years old.

Capacitor is a quick and cheap test/solution. Compressor could be shorted, or shorted to ground.
Fan? Amprobe could help.

Have never known a capicitor to be cause of fuses overloading,
Try with the power turned off going over all high voltage wire connections tighten every connection with an extra little grunt. A loose connection might be the problem
Let us know what you find

Also a good cleaning of the condenser unit might help, good air circulation is always a plus