we removed our ceiling fan and want to replace it with a regular light fixture. We have two black wires, 2 white wires and a green ground wire in the ceiling from the fan. We have tried various connections with the light fixture and either get a light that comes on with the breaker and doesn't work with the switch or no power at all. Which set of black/white wires do we use. How do we tell which set of wires goes to the wall switch? Any suggestions would be appreciated.