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Why is My Furnace Blowing Cold Air When the Heat Is On?

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As the chilly winter season arrives, a malfunctioning furnace can leave you feeling frustrated and uncomfortable. One common issue homeowners face is when their furnace blows cold air instead of warm air, even when the heating setting is on.

In the latest blog from the team at Chesterfield Services, we will explore the possible reasons behind this problem, and provide troubleshooting tips to try at home. However, sometimes furnace issues are too complex for untrained homeowners, and there’s no shame in calling Chesterfield Service for furnace services.

Common Reasons Why Your Furnace Is Blowing Cold Air

Several factors can contribute to a furnace blowing cold air. Understanding these potential causes can help you identify and resolve the issue. Here are some of the most common causes for furnaces to blow cold air:

  • Thermostat Setting: Check if your thermostat is set to “heat” rather than “cool” or “fan only.” While it might seem silly, the thermostat is always the first thing you should check. An incorrect setting can result in your furnace blowing cold air.
  • Dirty Air Filter: A dirty or clogged air filter restricts airflow, causing the furnace to overheat and shut the burners down. As a safety measure, the blower continues to run and blows unheated air.
  • Pilot Light or Ignition Issues: If you have a gas furnace, a malfunctioning pilot light or faulty ignition system may prevent the burners from igniting, resulting in the circulation of cold air.
  • Blower Motor Problems: A malfunctioning blower motor or fan can prevent the warm air from circulating properly, leading to cold air being blown out.

Troubleshooting Tips for Fixing Your Furnace:

A furnace blowing cold air is not an uncommon problem, especially when you’re turning on your furnace for the first time this season. The first thing to do is to check the thermostat settings. If the thermostat is not on at all, reset the furnace and thermostat with your circuit breaker.

The air filter is also a common culprit. For maximum performance, your air filter should be changed every 90 days, or three months. A dirty air filter can cause your furnace to overheat and prevent fresh air from entering your heating system. Once you replace the filter, see if that restores warm air to the vents.

If you still don’t feel warm air, check the pilot light is lit. If it’s not, follow the manufacturer’s instructions to relight it. If you have an electronic ignition system, consult the manual or consider calling a professional.

If you can hear the furnace start up again and stop shortly after, it could be having an issue with short cycling, which you’ll want a professional HVAC technician to address. If your pilot light can’t light at all, check to see if your gas supply pipe is opened.

Try other gas-using appliances in your home like a stove or a water heater to see if they’re working. Call your local gas company if you think there is an issue with your gas supply line or if there is a local outage.

If you put your hand to the vents and you can’t feel any air blowing at all, you might have an issue with your air handler or the blower fan that is causing issues.

When It’s Time to Call Chesterfield Service for Help

If you have attempted the troubleshooting steps without success or if you encounter any unfamiliar or complex issues, it’s time to call Chesterfield Service for help.

Turn off your furnace and don’t use it until these issues can be addressed. More attempts to run your furnace can cause worse damage and higher repair bills.

It’s especially important not to use your furnace if you also notice loud noises or strange odors coming from it. Burning odors are often signs of an electrical issue and could lead to a fire. You also don’t want to run your furnace when it’s blowing cold air because incomplete combustion could cause carbon monoxide poisoning.

If you are having furnace issues, make sure you have carbon monoxide detectors installed around your home to alert you in the event there is a leak.

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