I have a gas pack and I need to find out if the heat exchanger is under warranty.
It is a comfortmaker, Mod# PGAA24DIKG, SN L973826975. I have found out that the SN is directly related to the systems warranty. The new part is about $600, and I would like to avoid this cost if it is warranted still.

Most have at least a 20 year heat exchanger warranty on them. Any Comfortmaker dealer can get this info for you and arrange for replacement. Of course, you will pay for the labor to install it unless you are comfortable doing it yourself. Comfortmaker may require that you have a trained technician install it though...