Have a Armstrong Model G1N80AU075D12A-A furnace, Serial# 8400G26646 which was installed new in January 2005; and had a service tech tell us yesterday that we had a crack in the chamber; and therefore need to replace it. But he really thought we should replace the whole furnace again. It's only a little over 8 years old. What's the warranty on this furnace?? Any help would be appreciated. Thanks. Arnold Walker