It sounds to me like your battery voltage is down. Are you plugged into grid power? Is your charger/converter working? Do you have a Use/Store switch and is it properly positioned? Do you have a solar system?
If the refrigerator is erratic, and the furnace too, I think you are running low voltage on the 12 volt
side. If you had solar, it might charge enough during the day to operate things, but as soon as the sun goes down, nothing.... Assuming you are not on grid power that is.
If your converter/charger was not operating right, or your use/store switch was set wrong, it could do the same thing, even plugged into grid power.
So, more information is needed.