dmw

My 06 Legacy sedan's multifunction display periodically goes blank on me, then goes to a blinking display showing just "acc". Can't be changed until you shut the car off, then is ok. Seems to be related to how long and warm a trip it is (happens after 1 or 2 hrs continuous driving only, and not so much when very cold out.) Dealer says, huh. Of course he hasn't actually seen it happen. Ideas? Any ideas what the "acc" code signifies?