Why Your Furnace Is Blowing Cold Air: 10 Reasons & Fixes
There’s nothing worse than expecting warm air and feeling a chilly breeze from your furnace. However, it’s a pretty common issue, so no need to panic. If you’re wondering, ‘Why is my furnace blowing cold air?’ this guide will walk you through common issues and furnace troubleshooting tips.
Oftentimes, it’s a pretty simple thing to fix, and you probably won’t need to replace the whole unit. In this article, we’ll take a look 10 reasons why this happens and how you can fix them!
Common Causes of a Furnace Blowing Cold Air
If your furnace is blowing cold air, it’s a sign something isn’t working as it should. From thermostat settings to dirty filters or mechanical issues, several factors can cause this frustrating problem. Let’s explore the most common reasons and how you can fix them to restore warmth to your home.
Incorrect Thermostat Settings
If your thermostat is set to "Fan On," your furnace will keep blowing air, even when it’s not heated. To fix it, switch the thermostat to "Auto" mode, and make sure it’s set to the right temperature. This way the fan only runs when the furnace is actually heating. This is one of the simplest steps for how to fix a furnace blowing cold air
Dirty Air Filters
Clogged air filters can block the airflow from your furnace and make it work harder than it needs to. When it overheats, the safety HVAC system kicks in and shuts off the heat supply, leaving you without heat.
The easy fix is to replace your air filters every 1–12 months to maintain regular airflow. How often you need to change the filter depends on the type of filter you have. Dirty filters are often the culprit when a furnace is blowing cold air but running.
Pilot Light Issues
If your pilot light is out, you either might have a draft in your home or a faulty thermocouple. This senses the flame and keeps the gas valve open. If the light won’t stay on, try relighting it. A pilot light problem is a common reason for cold air coming from furnace vents.
However, if it keeps going out, we recommend calling a technician.
Malfunctioning Lighter
Modern furnaces use igniters instead of a pilot lights. If you don’t have a functioning igniter, it won’t light the burners, and you’ll be stuck with cold air. Unfortunately, this isn’t something you can fix yourself. You’ll have to call a professional who can replace the faulty igniter and get your furnace back up and running.
Furnace Overheating
If your furnace is overheating, it should trigger a safety mechanism that shuts off the burners.
It’s likely overheating because you don’t have good airflow or some of your components are dirty. If this is the case, start by cleaning the system, checking for any blockages, and replacing your dirty filters.
Fuel Supply Issues (Gas or Electric)
If your furnace isn’t getting enough gas or electricity, it not going to heat properly.
If you have a gas furnace, you can check the gas valve to make sure it’s open and the supply isn’t interrupted.
On the other hand, if you have an electric unit, make sure the breaker hasn’t tripped. If everything looks good and the furnace still won’t start, call your local technician for further inspection. Fuel supply issues are often overlooked during furnace troubleshooting cold air problems
Blocked or Leaky Ductwork
Blocked or leaky ductwork can send cold air through your vents instead of warm air.
If your system’s ducts are obstructed or have leaks, the heated air will escape before reaching your rooms.
This is why we recommend making it a habit to Inspect your ducts for any blockages or gaps and seal them up. You can also hire a professional to come in and clean and seal the ducts for a more thorough solution. If your furnace is blowing cold air in the house, leaky or blocked ductwork is a likely cause.
Faulty Limit Switch
The limit switch is made to control the temperature inside your furnace so it doesn’t overheat. If it malfunctions, it can cause the system to blow cold air or shut down entirely.
Since replacing a faulty limit switch requires expertise, we recommend calling a professional to get it fixed safely. A malfunctioning limit switch is another common answer to why your furnace blows cold air sometimes.
Insufficient Furnace Size
If your furnace is too small for the size of your home, it’ll naturally struggle to meet your heating demands. Insufficient furnaces can’t distribute heat efficiently. So, if a technician tells you your furnace isn’t the right size, the best solution is to upgrade to a properly sized one.
Aging Furnace
As furnaces get older, they naturally become less efficient.
If your furnace is 15–20 years old, it might be the right time to consider a replacement. Unfortunately, most older units can’t keep up with modern heating demands of modern heating. If you’re sick of making constant repairs, replacing it with a newer, more efficient model will save you both time and money in the long run.
Bonus Tips for Troubleshooting
Before you call a technician, there are a few things you can take to troubleshoot the issue yourself. These HVAC troubleshooting tips can often save you time and help identify the issue before calling a professional.
First, check for power problems. Start by making sure the furnace is plugged in and the circuit breaker hasn’t tripped.
Next, inspect your vents to see if anything is blocking airflow. You’d be surprised at how big a difference even the smallest foreign objects can make.
Finally, listen for any unusual noises, such as rattling, buzzing, or clicking. These are often signs that something is loose or malfunctioning.
A little bit of detective work can often reveal the problem and save you a service call!
Of course, if the issue persists, it’s best to put your pride aside and contact a pro.
When to Call a Professional
If you’ve checked your filters, vents, and power and you still have cold air blowing, it’s probably time to call in the big guns.
We always recommend calling a professional if you’re hearing unusual noises, smelling gas, or dealing with an old furnace.
With the Midas touch of a professional technician, you’ll be able to get your issue fixed correctly the first time. When you can’t figure out how to fix a furnace blowing cold air, a technician can provide the furnace repair tips and expertise you need.
Final Thoughts on Fixing a Furnace Blowing Cold Air
So, obviously, there are plenty of reasons your furnace might be blowing cold air, but don’t let that overwhelm you. Most of these issues are easy fixes with a little troubleshooting.
However, if your furnace is still blowing cold air after troubleshooting, contact us for expert HVAC repair services in Vancouver, WA!
