I have a Water Furnace Premier from 1992. Yes, I know it's old. I've replaced compressor and fan motor in the past four years. A week ago, we noticed A/C couldn't keep up to set temperature; Stage 2 on all the time; no fault lights. Local WF dealer says the Coaxial Heat Exchanger has a leak. He said the part is no longer available. He recharged the A/c; total cost $473. Six days later, it's doing the same thing. Tepid cool. Set at 74 degrees and at 10:30 in the morning, it's only cool to 75 degrees and at Stage 2. First, I don't feel I spent $473 last week very wisely. Secondly, is that part REALLY no longer available?
R22 equipment is really not longer supported. How much money would you invest into a 25 year old car, where the cost of a single repair exceeds its value? Don't get me wrong, geo heat pumps should last longer than 25 years, and often do. But sometimes you have to get a new one earlier. Good news would be that the newer ones are much more efficient, so over time it helps you to pay you back.
Coaxial refrigerant / water heat exchangers are fairly generic, so there is a good chance an aftermarket one could be found to fit the system. That said, it would take a fair bit of research to locate, for which the dealer would need to be paid. R22 is on its way out; has been for years, but EPA is now really putting the screws to production allocations, so prices are through the roof - it's time to get off that treadmill. Unfortunately "new" refrigerants R410a and 134a are also on the chopping block in the not too distant future...