I have a 1990 infiniti and I can't get the a/c to work! I replaced the whole electrical unit and it still doesn't work. Any suggestions on what might be the problem?

Have you checked to make sure that the system has an adequate freon charge? If it does, you will probably have to get a shop manual and follow the prescribed trouble shooting sequence or take it to a shop. On some cars the computer controls the power to the AC.

If it is low on refrigerant it could be out on the low pressure switch. You could try bypassing that switch momentary and see if the compressor kicks in.Like Dr D said it could be many things. There is a sequnce to troubleshooting that can be over the head of diys