There's usually two motors in the condenser unit, well, one is the compressor; the other is the fan motor. Is either coming on? I'm assuming you changed the fan motor, as replacing the compressor is usually beyond the average homeowner (specialized tools including gauges, vacuum pump, recovery system, etc.). Is the 24vac getting to the unit? That pulls in a contactor which starts everything running. You might be able to hear a click if someone operates the thermostat. That will work even if there's no power to the condenser unit.