Why does the compass mirror "boot up" with temperature readings?

[exsterminator]

When you start the car, the compass mirror shows 100 degrees C/F and then reverts to the compass bearing. Does this mean that the temperature can be displayed on the mirror? It would seem like it could so how do you get it to do that? And can you switch back and forth between temperature and direction?

I asked this in my last thread and verbalkint said he didn't think it could be done but it seems like you should be able to . . .

[China Man]

No, it's not possible.

I believe the reason for the temperature display in the LCD is due to the fact that the manufacturer of this compass mirror also makes mirrors for other makes, and those other makes support a temperature readout in the mirror. BMW does not.