I want to let everyone out there know that I just had my 7 year furnace serviced and found out that the heat exchangers were cracked! It is a Payne Plus 80 furnace made by Carrier. The service guy who came out immediately asked how old it was and before even opening it up said that models between '92 and'97 were installed with defective heat exchangers. If you have one of these please get a service gut out asap. This is a serious defect and I don't know why Carrier isn't letting everyone know about it. Of course, I had to pay $400.00 labor to have this fixed.