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Main Stream October 2017 Blog Freezing Inside

Why Is My Furnace Blowing Cold Air?

New England’s long, cold winter days are quickly approaching, and when they arrive, you’ll depend on your furnace to fill your home with warm air. But what does it mean if your furnace is blowing cold air? In this month’s news, the heating experts at Main Stream Mechanical share 6 common reasons why your furnace is blowing cold air.

My Furnace Is Blowing Cold Air. What Do I Do?

There are a few quick checks you can do before calling a home heating specialist. Take a minute to go through this troubleshooting checklist:

Main Stream October 2017 Blog Setting Thermostat 2


If your thermostat fan is set to the “on” switch, your furnace blower will run constantly even when your furnace isn’t heating the air.
 ~ Solution:  
Set your thermostat fan setting to “auto,” and your furnace will only blow warm air.

Have you recently installed a new thermostat? If you did it yourself, you may have chosen a thermostat that is not compatible with your heating system.
 ~ Solution:  
Contact the professionals at Main Stream Mechanical for advice.  

If you’ve had your thermostat for a while, the batteries may be low. Try changing the batteries with some new ones.


If your air filter is dirty, the flow of air into your furnace will be restricted, causing your furnace to work harder to push air through. This can create an overworked system, eventually causing your furnace to overheat and your burner to shut down. When your burner shuts down, your furnace will blow cold air.
 ~ Solution:  
Change your air filter to create an efficient, warm airflow.


If you have an older furnace with a continuous pilot light, its pilot may have been extinguished. The pilot light is used to ignite a larger flame that is responsible for heating the air that is blown through your furnace.

 ~ Solution:  
Relight your pilot light. If it fails to light or won’t stay lit, call a skilled HVAC technician at Main Stream Mechanical to assist you.


If you have a newer furnace with an electronic control panel, you may need a system restart.
 ~ Solution:  
Turn your furnace off at the power switch. Wait a few minutes, then turn it back on.


Sometimes there is nothing wrong with the heating part of your furnace and instead, the cold air is caused instead by the heat delivery system. The most common sources are holes or leaks in your ductwork, which allow warm air to escape and cold air to enter.

Broken or peeling duct tape, broken mastic or ductwork that is not screwed together may fracture at the seams, leak, and become inefficient. Closed duct dampers also inhibit airflow and allow only a trickle of warm air through the registers, even though the fan is blowing.
 ~ Solution:  
If you have any of these conditions, they need to be checked and rectified by an HVAC professional. Contact Main Stream Mechanical to schedule a service appointment.


If your burner is neglected, a buildup of grime and debris can cause ignition problems. Have your system professionally cleaned to take care of this problem.

If you’ve gone through this checklist, and your furnace is still blowing cold air, it’s time to contact the licensed and insured professionals at Main Stream Mechanical.

The Importance of Annual Heating Maintenance

Many causes of furnace problems can be prevented with annual heating system cleaning and maintenance. And, contrary to what you may have been told, gas-fired systems require annual maintenance too!

Furnace and Heating System Service and Repair in Massachusetts and Southern NH

If your furnace is blowing cold air or otherwise giving you trouble, contact the skilled technicians at Main Stream Mechanical who will address your heating concerns. Mention this article and receive $20 off any heating repair service provided by the Main Stream Mechanical team. When you schedule a service call, the licensed and insured professionals from Main Stream Mechanical will get your furnace or heating system operating at peak performance. For all your furnace, heating, water heater, plumbing, and generator needs; as well as heating and plumbing maintenance, service, and repair, we are your go-to provider! And, don't forget we install all kinds of residential and commercial heating and HVAC systems. In Haverhill, Amesbury, Newburyport, Rowley, Topsfield, Boxford, and other locations across Massachusetts and Southern New Hampshire, call our expertly trained technicians today at (978) 834-0849 or send us a message through our contact formSee our full-service area list for towns not noted.

For all your home and commercial furnace and heating system needs, or to receive a no-obligation consultation, contact us today!

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