As a heating system specialist with years of experience in diagnosing and resolving various heating issues, I understand how frustrating it can be when your heater is not functioning as it should. There are several reasons why your heater might be blowing cold air into your home, and I will outline some of the most common causes and solutions below.

Firstly, it's important to check the thermostat settings. Ensure that the thermostat is set to "heat" mode and that the temperature is set higher than the current room temperature. A common mistake is to accidentally set the thermostat to "cool" or a lower temperature, which would result in cold air being circulated.

Secondly, the air filter might be clogged. A dirty air filter can restrict airflow through the system, causing the furnace to work harder and less efficiently. This can lead to cold air being blown into the rooms.
Change the air filter and see if your furnace starts only blowing warm air.

Thirdly, there could be an issue with the furnace's heat exchanger. The heat exchanger is a critical component that transfers heat from the combustion gases to the air that is circulated throughout your home. If the heat exchanger is damaged or malfunctioning, it can cause cold air to be blown out. **Repeated overheating will hurt the furnace's heat exchanger, which is expensive to fix.**

Fourthly, if you have a gas furnace and it's only blowing cold air, then the pilot light may be out. The pilot light is a small, continuous flame that ignites the main burner when the thermostat calls for heat. If the pilot light is out, the main burner won't ignite, and no heat will be produced.

Fifthly, there might be a problem with the ductwork. Leaks in the ducts can allow heated air to escape before it reaches the rooms, resulting in cold air being circulated. Inspect the ducts for any visible signs of damage or leaks and seal them if necessary.

Sixthly, the furnace's blower motor could be malfunctioning. If the blower motor is not working properly, it may not be able to push warm air through the system effectively. This could result in cold air being blown out.

Lastly, there could be an issue with the thermostat itself. If the thermostat is not functioning correctly, it may not be sending the correct signals to the furnace to produce heat. Consider replacing the thermostat if it's old or seems to be malfunctioning.

In conclusion, diagnosing the problem with your heater involves checking the thermostat settings, air filter, heat exchanger, pilot light, ductwork, blower motor, and thermostat. It's crucial to address these issues promptly to ensure your home remains warm and comfortable, and to prevent further damage that could lead to costly repairs.

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Solution: Change the air filter and see if your furnace starts only blowing warm air. ... Repeated overheating will hurt the furnace's heat exchanger, which is expensive to fix. 3) Pilot light is out If your gas furnace is only blowing cold air, then the pilot light may be out.read more >>