Without knowing the history of how you got to this point...A couple,of things to look at or think about:
--is the evaporator icing up when the compressor runs? (You should see ice forming on the evaporator lines)...if so, suspect a bad temperature sensor
--if your old compressor gutted itself and blew metal shards into the system (which may not have been flushed well)...suspect clogged orifices in the expansion valve (and get everything properly flushed before you damage the new compressor)
--recheck and jump/bypass each of the high/low/cycling switches to see if the compressor clutch will engage...further, check or replace the AC compressor relay with a known good part
--double check exposed AC wiring for breaks or shorts to ground
--put the gauges on it and doublecheck the Freon charge
Good luck.