Needs new heat exchanger. Upgraded entire system to 5 ton HVAC Heat pump while initially looking at just replacing the heat exchanger. Room additions increased house square footage and a 4 ton system was running all the time. Used the opportunity to up grade my entire system. #s for Carrier system. Model # 58MXA100-13116 Serial # 3200A00451 Will sell parts if no one wants the entire system.