The answer to 'why is my heat exchanger not cooling' is that the heat exchanger may be malfunctioning or blocked, preventing proper heat transfer and cooling. Common causes include corrosion, cracks, or buildup of dirt and debris. Symptoms include poor heating performance, strange noises, or increased energy bills.
In many cases, the heat exchanger will need to be repaired or replaced by a professional HVAC technician. Attempting to service the heat exchanger yourself can be dangerous due to the risk of gas leaks or electrical issues. It's best to call a licensed HVAC contractor to properly diagnose and fix the problem.