We had a technician come out today to diagnose a problem with our furnace and upon inspection he noticed that there was a crack in the heat exchanger and the blower control board needs replacing (the original problem). The furnace (Lennox G26Q3/4) was installed around 1996. According to the tech, the heat exchanger is under lifetime warranty and we would have to pay for the blower control board. We would have to pay for the labor which he said would take a day to do. Does it make sense to replace the heat exchanger or should the whole furnace be replaced. I was also reading in another thread and it was mentioned that carrier gave an allowance if the heat exchanger needed to be replaced. Does Lennox offer something similar? Thanks for the help.