AC not kicking in

Did a compressor change an all the other things as well dryer exc. Charged system. Compressor is not kicking in. Bypass low psi switch an high psi still nothing. Checked all fuses inside an out, went to relay found what pins was what an checked have b+ ground comp and last was key well the key side has no voltage. I can apply voltage and kicks in. So thought okay has to be in head unit. Found a used unit tried it still nothing. I was wondering if the body control mod could be a problem or anybody have any other tricks for me to try?