I'll say it again, until you know for a fact that your system has the correct freon charge, you're wasting your time as you won't have voltage to the compressor until then.
Some older cars compressors can be breifly jumped by low pressure switch with no freon in the system but that's not always going to work with all cars as on some the other switch is also wired into the circuit (needs freon pressure in the system). I've seen guys baffled by this before, same as what you're describing here and once the system had freon, it worked.
A wiring break as you're now thinking would be very unusual but if you're absolutely certain that your system has the proper (full) charge and that you then have an electrical problem, I would then use the OEM Volvo wiring diagram to troubleshoot the electrical problem, not a Haynes or other "generic" manual as they're very bad IMO. You can buy the OEM wiring manual for your car by calling 800-25-volvo