Outside temp LED blinking

Hello again
Sometimes the outside temp LED blinks when I start the car (or in the middle of a trip).
I enter the system in '01, and it jumps from "07" to "15" back & forth.
Does anybody know what this code means ?

Thanks in advance

leov8@fibertel.com.ar
1990 V8 Automatico / 240 K and still running
(in Buenos Aires)