You have established that high and low voltage are present at the outside unit, good start. I have addressed and corrected the same problem a few times in the last month. Contactor -you replaced-. Tripped pressure switch will break low voltage -locate within cabinet and see if there is a reset, usually a red button-, this will require a later refrigerant pressure check. Low amps on the low voltage -check connections on either end of the wire as well as any splices between the two, it can be pinched and still look good so total replacement with new 18/2 is something to concider. After checking the above I would be suprised if the system doesn't work.