Overcharging 16.0v

Get out your digi meter and do some checking. What you are looking for is "voltage drop. Get the car running at a high idle with the battery charged, and make these checks with all accessories off, then repeat with the headlights, heater, etc, on

Stick a meter probe DIRECTLY onto the battery negative post. Stick the other probe directly onto the case of the regulator. You should read VERY low voltage, the lower the better (zero is perfect) If you read more than .2 (two tenths of a volt,) you have a ground problem.

Stab a probe directly onto the battery positive post. Stab the other onto the ignition terminal of the regulator. Once again, you should read very low, the lower the better, same as above.

Pull your battery terminals and CLEAN them.