I have power at the compressor but the compressor will not come on. my pressures are 45 low 200 hi side.

 

Another thing I make sure of is that the condenser coil is not clogged up with debris and that the fan is working properly that cools the condensing coil if it has an independent electric fan. On older vehicles the fan can seize up or the brushes can be worn down to nothing.

 

Might be an orifice tube problem. Could also be the ECU issue as well.