Since I purchased it, the dash needed the steppers motors replaced so figured I'd go through the little remaining things once I got started. The batter has been disconnected more than once, made no difference.How long has it been this way? Have you tried disconnecting the battery over night then reconnecting to see if it’d reset?
I've read through a few, in those cases as you mentioned the display was intermittent. In my case the display never goes off unless I intentionally turn it off, otherwise it stays lit constantly. The buttons seem to work as expected, it allows me to set the temp F or C, the zone and I can also put it into CAL mode, it just appears that when not doing anything in specific it defaults to lighting all segments in the display.I posted a topic on how to fix the compass and temperature display a few.years back on my 2001 suburban. The display was intermittent. I think I pulled the mirror and resoldered the cracked and loose solder joints. Try the search option.