Hopefully I can get a little help

My Parents can leave several to scratch their heads. I just suppose that they grew up in a different time, and they have become accustomed to their own methods and ways. I myself have found my guys thinking about my Wife Mary and I the same way, so I understand it a bit. I try not to supply them a taxing time about the way they like to do things, because I suppose I have certain stubborn practices that I don’t want anyone to force myself and others to not do either. However, occasionally their preferences have myself and others anxious about their health. As such, they have had the same home for over 40 years now. By this point, both their undefined and gas furnace are certainly shot as well, but living in a Southern temperature does alleviate some concerns over them not having a functional central gas furnace in their home, yet I still do worry about their health when the uneven temperatures get actually low. In fact, my wifey and I tried an experiment where we would go a month separate from using our central heater. Both of us live around the same area, so our temperatures are actually similar. Both of us did use section furnaces as they do, however we couldn’t make it more than 3 afternoons before we caved and turned up our control unit. Afterward, I went ahead and called my Parents to beg them to look into superior heating systems for their home. I even begged them to let us have an Heating and A/C specialist supply them an estimate on fixing whatever issues present with their Heating and A/C system. Both of us told them we would cover all costs, but, of course, they said they were thrilled just the way they were!

HVAC unit