Airconditioner wont come on

You need to start with a volt meter. check the power first at the disconect then follow them wires inside the unit to the contactor check them were they connect on the contactor. then check them on the other side of the contactor. it there is no power there find your transformer check and make sure you got 24 volts if not you need a transformer or maybe just a fuse. does your indoor fan run? compressor and outdoor fan will usually run together. look at your wiring diagram and check voltages at each control device. if your indoor fan runs push in the contactor and see if the compressor comes on use a stick so you dont get shocked. So to sum things up if nothing works problem is probably transformer or tstat or main power. If compressor and outdoor fan don't work could be contactor or capacitor if one of outdoor parts runs but not the other then that individual motor could be devective. but it could also be out on a control such as low pressure switch (low freon)

Does the indoor blower come on? If not you might have a low voltage problem in your thermostat circuit or blown breaker or fuse for your furnace which energizes the contactor outdoors. If indoor blower runs check if their are any fuses in your outdoor disconnect.