Land Rover Repair: 94 range rover lwb A/C

Question
Hi 94 range rover lwb, ac compressor will not engage. It is fully charged. relays are fine, ac diode pack, i have no idea how to test. I did have an alternator failure, while driving all went dead slowly. Then all off, i heard many relays clicking away under dash as it had so little voltage. replaced alternator. ac clutch not engaging. There are two wires to dryer, I assume pressure switch? two more wires branch off from this and go nowhere but they have an end that has a jumper wire on it? it will cycle clutch with my friends tester connected to pressure switch, even though it is not 12 volt powered test light..this seems so odd. also i just replaced with rebuilt engine as well. is there a ground for ac someplace. or is there some fuse unknown to me(fuse link) help

Answer
The wiring diagrams for that car are in a separate electrical troubleshooting book - they are not in the workshop manual.  Get an electrical book and trace the power and ground.  There is no computer in the circuit; it's a matter of following the signal from dash switch to pressure switches to compressor, etc.   I expect you will find a broken connection, either in a supply or ground.  It's common to have connection troubles in the fusebox itself.