Though your AC unit might work after a coolant refill, that’s a band-aid fix for a much larger problem. Because air conditioners are closed systems, any loss in refrigerant means there’s a leak somewhere. With many older systems using environmentally hazardous substances like 410A which is now banned in new units and only available via reclamation getting these refills can end up being more expensive than buying a new air conditioner that uses safer, lower-cost refrigerants.