Climate, clock, radio, speedo backlights, all in sync. I think I've got a bad connection somewhere, likely having to do with the brightness dial to the left of the steering wheel. Has anyone encountered this before, and is it an easy fix? I figured this would be a common thing, but my searches haven't turned up anything.

It doesn't appear to be battery related - just random dimming / brightening. I can really make it dance if I fiddle with that horizontal wheel.

 

It is probably a bad light dimmer switch(the horizontal **** you are talking about) or the connection is poor. I would pull the cluster binnacle off - CAREFULLY- the plastic is very fragile and check the connection at the back of that switch. If the connection is good, start with a new one