During an annual furnace tune up, the technician observed the CO reading was 75. He told me that it was still below the 100 mark so there's no cause for alarm. But the higher CO reading is caused by an aging heat exchanger that rusts over time. The unit, a Carrier 58MVP080-14 propane furnace, is 13 years old. The heat exchanger is not cracked. The unit has and still performs well. Aside from annual tune ups and routine filter changes, the unit has never given me any trouble. The tech however recommended that they send out a "comfort analyst" to evaluate the home and replacement should be considered. Replacement of the heat exchanger was discouraged due to the age of the unit.
I'm pretty sure I could replace the heat exchanger myself but I'm wondering if I should. Should I do anything? Or should I consider replacement?