... accuracy of the console voltmeter, but can i tap into the wiring harness with a good DVM and get an accurate reading. by tap into, i just mean connect the leads of a good DVM into the connection terminals. i want to check a possible charging fault.

Connect the DVM across the battery terminals directly if you're looking for a charging fault. Should be 12.5 at rest, 13.5-14.5v engine running at any speed. If you don't get those numbers, start tracing other places, including the regulator, the charging lamp, and fuse 8 (or 9, can't remember which). The problem with the OEM voltmeter isn't so much the meter, but where it's connected into the harness.

Use a good meter, across the battery posts. No, not the clamps--the posts themselves. That will give you a good clue as to the health of the charging system. 12.6V is what a "full" battery has; you should see at least 13V at idle with no big load on the system and hopefully about 14V over a couple thousand RPM. Loads on the electrical system (e.g., headlights on, etc.) will reduce that number, but it shouldn't get down to 12.6V at anything but idle even with all the electrical goodies on.

--DD

That gauge will read the best with a direct hook up at the battery....but WILL draw it down if left for more than a few days.

You will get a slightly less accurate read if hooked thru a ignition switched terminal on your fuse box....but no draw down on the battery from an always powered gauge....

12.5 rest FULLY CHARGED
12.5-13v at idle
13.5-14.0v at 2500 rpms

What everyone else said. Plus to elaborate on Dave's response, turn on every electric item you can. Headlights, highbeams, radio, emergency flashers, fresh air fan, heater fan, step on the brakes, etc. Put as full of a load on the charging system as you can. Then check volts at the battery, both at idle and 2k+. If you are getting below 12 volts you can shut off a few things to see if the volts come up. You may have a charging system that is on the edge of providing the volts required to keep your battery topped off. This can be due to faulty wiring/grounds or failing alternator.

-Jeff