Climate control blinking light?

[Martin W. N. Suryadarma]

Hi all,

1 more question from me. My car is 1989 Audi 100. You know on the climate
control, on the top right corner, there's that button for Outside Temp
right? Next to it there's a red light. If you press the button, the red
light comes on. Sometimes, after I start the car, that red light
starts blinking. Pressing anyting won't help. But it'll go off in a while 
eventually. This just happens very randomly. Any ideas why? TIA!

Martin