hello friend i have early phase mention about the invention of ac today i will share about repair and maintenance of  AC and refrigerators but first we need to know about the type of refrigerator available in world which mainly 2 type 1)direct cool 2)frost free  Direct cool are those refrigerators which has single door but frost free have 2 separate door first one is older while 2 is newer version of fridge frost free is melting down the ice within 8 ours of running automatically in freezer or in evaporators,while direct cooling c cant do this process automatically generally we need to use thermostat switch after 16 days or stop the fridge after 16 days and open the door for an 2-3 ours by which ice will automatically melt down. Air conditioner is mainly 3 type 1)window type(old type)split (new type) and package initially centralize ac come in our society then split and package