My son bought a 83 d 150 ind it has a charging system problem it had a new alt on it and wasnt charging . so i put a used alt i had on it still not charging so i put a voltage regulator on it stared charging went to 14.6 at first then slowly back down to 11.9 . so i switced the field wires around and it started charging went to 13.6 and the voltage regulator would start kicking in around 12.3 and 12.1 and go to 12. 6 and kick out with a load on it it would stay at 12.1 is this to low ,