Not solved yet, but as Yogi Berra said, "You can observe a lot just by watching"

I drive a salty four-lane to work, so get bopped by salt pellets all the time.

It took this happening in place where I couldn't have been bopped to make it sink in, which is that when the speedo quits the first time there's a pip noise at the same time, sounds like something small, say a salt pellet, hit my windshield.

As it goes on and off after that there is no accompanying sound, just that first time when it stops working suddenly.

So I'm thinking that some device on the panel has a problem and goes out with a pip.

Any ideas?

I'm going to pull the panel tomorrow when it gets warm and have a look.