Alternator wiring problems

Hi my 63 has got a external reg alternator(both new) and seems to be charging at 15 volts which seems a bit  high, The dash light seems to stay on all the time even though i am getting a charge i removed it abd the voltage drops to 13 volts, also is the resistor in the guage cluster anything to do with the charging

the dash light goes out when the signal from the battery is the same as the signal from the alternator,,,,I am thinking that maybe the wiring on the starter relay might need cleaning,,,or could be the contacts in the ignition switch,,,,the probably yellow,  A terminal,  on the regulator, determines the voltage of the system,,,,,if it senses 13 volts at the relay,,,,it sends another volt to make it 14 and stop the charging,,,,,and that could make the voltage 15 volts,,,,,maybe try to run a jumper wire from the positive post on the battery and touch it to that 2nd A terminal in the regulator connector and see if your voltage changes,,,,,also do a jumper from the negative post on the battery to the base of the regulator to make a good ground circuit,,,,,you are testing for a voltage drop,,,,,,,see if you find anything,,,,,

Thanks for your help i will try that and see what results i get