A/c issue

[ehm]

Hello all, in my attempt to gain air conditioning after my system gradually petered out I have replaced the compressor, the control unit and the relay. (I’m better at throwing parts at a problem than diagnosing Lol). The system is basically empty and thoroughly vacuumed, and I cannot get the clutch to come on even after jumping the pressure switch. I was wondering if there is a way I can wire the compressor directly to the battery in order to get the clutch to come on in order to fill it up. there are four wires in that pigtail from the compressor, and if it is possible to connect directly to the battery, I don’t know which wires to connect…. Any help on this overall situation is welcome! Thanks! (1987 300sdl)