Yes, as suggested above, the regulator needs to be grounded......but a poor ground results in what you've just observed. So a poor ground will result in poor charging,
not over-charging. The reg is grounding the green field wire coming from the alt to generate the field in the rotor windings, controlling the duty cycle to maintain the set
voltage. If You're losing 1.2 volts, that could get You to 16V, and since that blue wire is powering the field, the more the reg grounds the rotor the more current it uses
helping to drop the local voltage there.
