I would first make sure there is power to the fan motor and that the 24v wiring is not disconnected. To test the capicitor, carefully disconnect the wires to it without touching the ends or letting them touch each other. Use an ohmmeter on the two leads to the capicitor A. watch the needle on the ohmmeter, if the capacitor is good it will go all the way up instantly and move back slowly B. if the ohmmeter has an audible signal it will go to a high pitch whistle and receed in a couple of seconds.
The problem may be with the relay. Tag the wires to it, take it off and take it to the local A/C and electrical supply house, they will be able to test it for you and replace it if necessary.