The cluster is grounded, and there are circuits that are energized all of the time that need the ground to be energized/lit. Usually when more than one circuit is energized but not completely it is something common to all, such as a ground, and the electrical path is in through one / out through the other. Since the dash has both; unswitched +12v and grounds, it is possible that the ground is weak. The instrument panel parts are grounded together mechanically also.

Try another thing: Release the bail and unplug the wires on your alternator. I don't know the year of your car, but I believe that all years can be unplugged in this way. A glowing alternator light with the key off could indicate a bad voltage regulator/alternator.

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Gone to the dark side

- Jeff