Im not sure what the regs are where you are, but here in Pa you cant even by the freon without being licenced. If the freon is gone, it pays to have them do a leak check first, (they will put a dye in the system. to find the leak,) It may be relay related also, on the 96 rodeo i had, theres a small canester behind the grill that i just jumpered the two wires to get the pump to run. If the freon is too low, it wont kick in automatically. atleast this way you could tell if its your pump clutch.....