The answer to 'my heat exchanger keeps shutting off' is that there are several common causes, including a cracked heat exchanger, issues with the gas valve, problems with the limit switch, or a malfunctioning thermostat. Symptoms may include the furnace turning on and off repeatedly, strange noises, or a lack of heat. Solutions can range from simple thermostat adjustments to more complex repairs like replacing the heat exchanger.
If your heat exchanger keeps shutting off, it's important to diagnose the root cause. Some minor issues like a faulty thermostat may be something you can troubleshoot yourself, but more serious problems with the heat exchanger or other components usually require a professional HVAC technician. Attempting complex repairs without proper training and equipment can be dangerous, so it's best to call in an expert if you're not confident in your ability to fix the problem safely.