what is this? a fuse I hope? since the vacuum and motor driven ones still work? the whole unit has been in and out of the dash before, for changing a bulb and worked fine. also, there is a beeping (warning-like) noise coming from it, that disappears only when the blinkers are engaged.

Check your fuses VERY CAREFULLY. Sometimes they can open up and it will not be obvious. They can be bad and still look fine because the metal corrodes and breaks over time.

Once I was convinced that my fuses were ok. I had a problem like yours. But when I touched the offending fuse, with the key on, it sparked a tiny spark and the cluster came back to life. Viola! The bad fuse.

Good luck

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2012 E350
2006 Callaway SC560

I think that's it too. the original fuses on these benzes are not very good I heard. My wife drives this car and she only saw the fuel gauge being very low. I asked her if she hadn't noticed the oil pressure, temperature and RPM gauges not working.
she then said:" what are you talking about?"