There are 3 aspects besides the regulator itself
1...Voltage drop in the circuit path from the battery to the regulator. The regulator will overcharge by the amount of this drop. Connect a voltmeter as close (electrically) to the regulator as you can get. Your 12V feed to the ignition system (ballast resistor junction) or the alternator blue field wire are probably as close as you can get. Turn the key to "run" with engine stopped. Put the other probe directly on the battery + post. You should read a VERY low voltage the lower the better. Anything above say .3V or so (3/10 of one volt) is voltage drop, and more is worse. What is HARD to check is the VR connector itself. Examine the VR connector and VR itself for corrosion, looseness, etc
2....Voltage drop in the ground circuit. The VR MUST be grounded electrically to "same as battery" negative. To check this run engine at fast idle, with battery up and normalized. Check first with all loads off, and again with lights, heater, etc on. Stab one probe directly into the VR mounting flange, to get through paint, rust, etc. Stab the other probe into the top of battery NEG. Here again, the lower the better, zero is perfect
3... In some cases the battery itself can cause this. Sub another known good battery and try it.
If these 3 things check out, replace the VR. It is rare for a VR to overcharge like this. Usually, they fail "no charge" or "full charge" meaning the voltage goes high and gets higher.
