relay that trips the 230 volt line. To test this, turn the inside thermostat all the way down and go to the outside unit and turn the power off to the unit (breaker box). Open the unit and see if the relay is engaging the 230 volt leads. If you are uncertain then take a wooden object and push down on the ceramic bar that connects the contactors. If it has play, you are not activating the 24 volt relay. To verify this, turn the 230 volts on, and again using a wooden (non conductive object) press on the ceramic bar and see if the unit starts. If so get a new contactor assembly. If it is o.k. then you either have a bad capacitor (the fan should turn slowly ) or a bad fan motor, If when you turn on the unit and it quickly trips the circuit breaker, you most likely have a bad compressor. In either case you should get professional help.