Absolute first thing is to see what the battery is actually running for charging voltage. Monitor it with a meter. With engine warmed and battery "normalized" meter the battery voltage at "low to medium" cruise RPM. Should run nominally 14V, 13.8--14.2
should NOT be above 15 in any case. Could be bad battery, wiring problems (search this board for "voltage drop") or a bad regulator, or if truly severe, might be some electrical problem, wiring or alternator, causing the alternator to charge at full output
To check for voltage drop make two tests:
1...Turn key to "run" with engine stopped. Stab one meter probe into the top of the pos. battery post, and the other as close as you can get to the VR IGN terminal. This is also the "key" side of the ballast. You are hoping for a very low reading, the lower the better. More than .3--.4V (3/10 of one volt) you need to be looking for the cause
The suspect causes for (1) is poor contacts in the ignition switch, or poor connections in the switch connector, poor connections in the bulkhead connector terminals, in rare cases the ammeter or welded harness splice. Could also be the VR connector itself
2....Make this test first with everything off, and again with loads turned on, lights heater, etc. With engine running to simulate "low to medium" cruise RPM, stab one meter probe into the battery NEG post, and the other into the mounting flange of the VR. Be sure to stab through rust, chrome, etc. As (1) above, the lower the better, zero is perfect. Much reading at all, you need to improve the ground to the VR. Unmount the VR, scrape the flange and firewall clean around the mounting holes, and remount with star lock washers. Sometimes you need to add a ground jumper between engine block or battery and the firewall.
