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Why Is My Furnace Blowing Cold Air? A Troubleshooting Guide

Why Is My Furnace Blowing Cold Air? A Troubleshooting Guide

Here in Pittsburgh, the weather is about to reach the coldest temperatures of the year. When the temperatures start dropping below freezing, we use our furnaces more than any other time of the year. So, if your furnace is blowing cold air on a cold day, it can quickly become a major issue. Not only is it an issue for your furnace and home appliances, but a lack of heating in the winter is also majorly stress inducing.

That’s why we’re here to discuss how you can troubleshoot your furnace in the event it stops warming your home. Often, there is an easily fixable problem that you may have overlooked. And, at the very least, if you can’t remedy the issue and need to call a professional, you’ll know where the issue is coming from.

Troubleshooting Your Thermostat

If your furnace is blowing cold air, it could be an issue with your thermostat

old thermostat dial
The solution to your furnace issue could be as simple as cleaning your thermostat.

One of the most common reasons your furnace is blowing cold air is an issue with your thermostat. Your thermostat controls your temperature, so it is possible that your furnace is functioning properly and is just receiving incorrect commands from your thermostat.

Dust can collect over time in your thermostat and will lead to transmission issues if you don’t clean your thermostat regularly. If you can't remember the last time you cleaned your thermostat, then it is likely time for a cleaning. To clean the dust out of your thermostat, simply dip a soft cloth in some cold water and clean out any visible dust and dirt. Do not use too much water or you could damage the electrical component. 

It is also possible that your thermostat is on the wrong setting. Usually, your thermostat will have three settings — on, off, and automatic. Though many homeowners may assume that “on” and “automatic” are the same settings, often the “on” button merely keeps your furnace running and not necessarily blowing out warm air. So, if you notice your thermostat is set to “on,” try out the “automatic” setting and see if the warm airflow resumes.

Finally, if you are still having trouble getting your thermostat and furnace working properly, it may be time to replace your old thermostat in favor of a new one.

You Need to Change Your Air Filters

Your air filters could be a contributing factor to your furnace blowing cold air

man removing air filter from furnace
It is easy to forget when you last replaced your filters, so make a note in your calendar.

If you’ve determined that your thermostat isn’t the issue, then your next step is to take a look at your air filters. Your air filters separate your furnace from your air ducts and catch any dust and debris that gets caught in the filter due to the air flow. You should change your air filters every 3 to 6 months to ensure that your furnace continues to function properly. However, it is easy to forget, and many homeowners do not realize they need to change their air filters until they encounter an issue. 

Should you forget to replace your air filter, it will eventually become clogged which will prevent warm air from reaching your living spaces. To remedy this, simply replace or clean your air filters. Depending on your furnace, you may have a filter you can wash with a garden hose or you may need to purchase a replacement.

Your Propane Tank is Almost Empty

If your gas level is too low it will cause your furnace to blow cold air

home propane tank with bush in yard
Be sure to check the pressure and gas level in your home propane tank. .

Another issue that will cause your furnace to blow cold air is that you are almost out of gas. Your furnace is powered by natural gas, so when that gas is nearly depleted, you’ll start to notice your furnace is no longer warming your home. 

To determine if this is, in fact, the cause of your inconsistent heating, simply open the gas valve and check on the gas level. For a personal gas tank, you should check to make sure the pressure is high enough to fuel your furnace. If you are hooked up to a shared gas line, call your neighbor and ask if their gas line is working properly. If the issue isn't coming from your gas supply, then the issue could be your pilot light.

Your Pilot Light is Out

Check your pilot light before you call a technician

furnace lit properly
If you are unable to locate your pilot light, you can always call a technician for further direction.

This is mostly a problem for older furnaces, so if you have recently had a furnace installed there is no need to worry about the pilot light going out. In these older models, the pilot light can go out, which means that your furnace will cease heating. Then once the fan turns on, you’ll feel your furnace blowing cold air. To fix this issue, you need to reignite the pilot light

First, locate a small knob near the bottom of your furnace. Then, set the knob to “off” for at least 5 minutes. After that, change the setting to “pilot” to turn on the gas. Then, set the knob to “on” to reignite your pilot light. 

If you’ve tried this technique and your pilot did not relight, you should turn off the gas and call a professional HVAC technician as soon as possible.

At Restano Heating, Cooling & Plumbing, we can address any furnace related issues in your home as we move into the colder seasons this year. If your furnace is blowing cold air and you can’t locate the cause, give us a call as soon as possible. We only complete repair work using experienced, licensed technicians who use professional equipment that meets our standards. So, give us a call today and let us make sure your heating system is running properly.