Why Is My Heater Blowing Cold Air?

During winter, the last thing a New England homeowner wants is a problem with their heat source. Yet if the furnace is not warming up or blowing cold air, there could be an issue with the gas supply, air filter, pilot light or condensate line. Understand potential sources and how to fix the issue.

Heater Is Warming Up

When a heater or furnace has been turned off completely, it needs time to warm up once turned back on. This can result in gusts of cold air but optimal performance should resume in 10 to 15 minutes. After this point, cold air could indicate an operational issue.

Improper Thermostat Setting

If your HVAC system is used for both heating and cooling, you need to switch the setting to “heat”. Also make sure the fan is set to “auto” instead of “on”. Otherwise, the system will continue blowing cold air in an attempt to cool your home and the furnace and fan will be out of sync, preventing the efficient circulation of warmth.

A Dirty Filter

A dirty filter can affect how air circulates through your HVAC system and cause it to overheat. In addition to its impact on performance, a filter clogged with dust and debris can prevent warm air from passing through the heat exchanger and reaching your home’s interior.

In turn, your home may feel cool with the heater on or like a draft is coming from the furnace. Eventually, the device shuts down once it overheats to decrease fire hazards and additional damage.

As a tip, check your HVAC system’s filter about once a month and change it once you spot visible debris. Generally, you’ll need to replace the filter every 90 days or once per season, based on usage.

System Overheating

You may notice that your furnace blows cold air before shutting down completely, which can be due to overheating. When this occurs, the heat buildup trips the furnace’s safety mechanism to prevent a fire or damage to internal parts.

While a furnace may overheat due to a dirty filter restricting air flow, it can also relate to:

• Dirt and dust accumulation throughout the furnace, including parts like the blower.
• Age; furnaces in use for at least 15 years have a higher likelihood of overheating.
• A mechanical issue, with one or more parts malfunctioning, such as the burner, flame sensor or gas supply line.

Pilot Light Issues

More of an issue for older furnaces, the pilot light helps the system generate heat, which a blower then distributes. With gas-powered furnaces, the pilot light is continually on. If it shuts off, the furnace stops generating heat and you just feel air from the blower.

Yet the pilot light might not be acting alone. Instead, the light going out may indicate a malfunctioning thermocouple or an insufficient supply of gas. This latter aspect could be due to available resources or an issue with the gas valve. Although the pilot light can be temporarily re-lit, you’re advised to have a professional fully assess the system to determine the source.

Clogged Condensate Line

Similar to a pilot light that has burned out, a clogged condensate line interrupts the ignition process and means your furnace isn’t generating heat. The blower continues to circulate air that feels cold when coming through the vents.

Leaking Ducts

The issue might not be with the furnace at all, but the ducts that transport air throughout your home. Disconnected segments or leaks cause some, if not a significant portion of the air generated by the furnace to escape.

This factor may stem from age, poor installation, damage or an animal residing inside your ducts. You’re recommended to have an HVAC technician fully assess your system for leaks and potential causes.
 
Has your heater or furnace been blowing cold air? Schedule a service appointment with the HVAC technicians at MJ Fahy & Sons today.