Alternator Full fielding..??

71 dart, o.e engine harness and connections. Checked all connections and batt voltage, all grounds look good. Field wires Not reversed. Double checked ign switch and tried a new one to test. Ok. Two regulators one new one used both act the same. Battery at 12.9 no load. Shoots to 18 volts at about 2k rpm. Stays high with any kind of rpm. New problem all components were working together prior to this….?? Any ideas..Thanks in advance….Swingn..