AC/Fuse or relay

Without knowing more it's impossible to tell. Is your compressor running? Is it getting voltage? Is voltage getting through low pressure switch? Could be fuse, could be refrigerant charge, could be compressor. What have you checked? One way to quickly see if it's low on refrigerant is to go to the low pressure switch, pull the plug off, and use a small bit of wire to act as a jumper and connect the 2 pins in the plug. If compressor starts running then it's low on charge. Don't leave the wire for long though.