Arrived on site to perform diagnostic on 10 year old package unit. Homeowner states system is not operational at all, fan is not even turning on and he believes there is a blown fuse up on unit. Went on roof and Checked package unit electrical and system components. System is recieving proper high voltage power, but no low voltage power present. Found a bad 5 amp fuse on circuit board not allowing system to turn on at all. Replaced fuse and tested unit to check for any electrical short. System cycled on and started running, fuse no longer blew out. Homeowner made comment that his system does not cool very well in the summer time. The system was here when he purchased the home. Performed thorough evaluation of system to figure out why system does not cool correctly. Upon attic inspection, found that ductwork is in horrible condition. Actually found that the return duct had completely came off the unit, and system is pulling all the air in from the attic and not from inside of the home,