Hi slnlb,
Welcome to the Heartland Owners Forum and sorry to hear about the failure on your A/C unit.
Dometic had a problem for a while after moving production to China and a number of people had A/C failures. Your unit may have been produced in the time frame where there was a relatively high failure rate.
Also, I think Dometic may have a 2 year warranty on the A/C units. Putting together the manufacturing problems they had, and the 2 year warranty, it's possible they might grant an accommodation for a failure occurring at 25 months.
You should call Dometic customer service at 800-544-4881 and discuss the problem and see if they will reimburse you.
Btw, my understanding is that when air leaks between the cold air output and warm air return, it can cause the unit to not cool well. But I don't think we've heard about units failing from that type of problem.