Q: Lost temperature control on hvac

Last week I disconnected the battery to clean posts and connectors. Since then I cannot control the temperature. I don't have the electronic push button system. Mine is the knob selectors. I first noticed that it wouldn't adjust for a cooler temperature in the cold weather we were having. Toward the end of the week it had warmed up. I thought I would try the ac. I turned the knob to cold setting and then selected Max Cool. Nothing but very hot air. Turned it off. When I got home, I left the temperature selection to cold. Now I have nothing but cold air. I read somewhere that this could be a simple reset issue after having disconnected the power. But I don't know if that was referring only to the electronic push button system. What I read indicated I will need a mechanic for this step. Does the reset also apply to my climate control system?