Speedometer Backlight doesn't dim in auto light mode

We've use the Auto position for he headlights most of the time since our 2008 was new. Not every time, but too often, the speedometer cluster lighting doesn't switch to dimmed setting when the headlights come on. It seems to happen most frequently when we are in a parade at night. The backlight for the radio dims properly with the Rheostat, but not the Speedometer Cluster. To get it to work properly, you simply need to turn he headlights off and back on again. (or today, open the door)

Sometimes the dim after a 5 second delay (after covering the sensor), and other times, they don't dim after a 20 minute drive in the pitch black.

So what gives? Is this normal?

The dealer, three times now, tells me this is normal operation for the Prius. And claims there is nohing to fix under the expensive extended waranty we paid too much for. I've been bringing this up almost every time we bring the car in... For more than 4 years now.

If you don't see why this would be a problem, turn your display to the brightest setting and go for a drive on a stormy night.

 

Found it here-> GSIC - Global Service Information Center

That the Combination Meter needs to be replaced if it doesn't dim with the Heater Control Pannel.