My Honeywell thermostat stopped working and it says "Hold -AC". We're freezing!? - honeywell chronotherm iii -ac

We have a Honeywell thermostat III thermostat (model T8600).
He always says "Hold 67" (or whatever temperature we set the time). Today, it appears that the thermostat reads "Hold-AC". No matter what the change to this screen. Our landlord has no idea what it means. Anyone have any ideas?