A central air conditioner runs on 220 volts of electricity. A connection must be made between the main electrical circuit panel in your home and the 
condensing unit in order for the air conditioning to run (large grey wire). A skilled licensed electrical contractor should complete the high-voltage wiring. Inexperience in this area can cause electrical shock or damage to your equipment or property.
The photo at right shows how the wiring should connect to the fuse/breaker box.
DO NOT attempt to repair this component on your own!
FYI Tech Talk: Some A/C equipment have fused disconnects and some are breaker disconnects. Looking the A/C unit, if the data plate says “Max Fuse XXX”, that means you must use fuses (not a HACR – Heating/Air Conditioning/Refrigeration breaker) because that is the way the unit was tested and listed.