First thank you for letting us know what's happening. So many times we try to help and never hear the outcome. Hate that! But I would like to know why your mother is going to change out the heater. Old doesn't mean bad. If it does then I'm really, really bad! I ask this because I've had customers who were up in age want new systems because of something they've heard, read or because they spend a hundred dollars a year on maintance. I'd usually gently told them that they were going to spend 2,3,4, 5 thousand dollars to save 10 or 20 dollars a month on utility bills or a couple of hundred for maintance every year. Sometimes their fears could be solved with a carbon monoxide detector, new evaporator or some less expensive way than replacing the unit. And sometimes what they had heard or read was either misunderstood or flat wrong. Of course, it helps to have an honest serviceman and not someone who's just out to make money. My customers were my friends and they held a wake when I left. Or was it a party?