The answer to 'why is my heat exchanger not cooling' is that the heat exchanger may be malfunctioning or blocked, preventing it from effectively transferring heat. This can be caused by a variety of issues, such as a buildup of dirt and debris, a problem with the blower fan, or a leak in the system.
Some common symptoms of a heat exchanger issue include the furnace not blowing warm air, the furnace cycling on and off frequently, or the furnace making unusual noises. If you suspect a problem with your heat exchanger, it's important to address it promptly to prevent further damage and ensure the safety of your home's heating system.