Why Is My Heater Blowing Cold Air? | Furnace Troubleshooting

Why Is My Heater Blowing Cold Air? | Furnace Troubleshooting

Anthony Barnes

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A heater is meant to blow out warm air to keep you warm. So, when it suddenly starts blowing out cold air, it can really ruin your day. Everybody wants to be comfortable in their own home, and when winter hits, our heaters play an important role in that.

But if they start blowing cold air, you may need some help from a professional heating technician. 

However, before you get the professionals involved, there are a few troubleshooting tips we can share with you. These steps should help you recognize what the issue is, and hopefully fix it yourself.

Why Is My Heater Blowing Cold Air Furnace Troubleshooting (1)

With that being said, there will be times when calling in a professional is the best course of action. When it comes to heaters, there is a lot that can go wrong. 

For each troubleshooting option, we’ll let you know what you can do about it. Hopefully by the end of this post, you will have a good idea of where to start with your malfunctioning heater.

If you would rather have someone come out and take a look at it, that’s fine, too. We know troubleshooting furnaces isn’t for everyone, so just give us a call to do it instead.

Why Your Furnace Might be Blowing Air That is Cold

Here, we’re going to go through some common reasons why your furnace could be blowing out air that is cold. As you read through these problems, don’t forget to think about how much time has passed between them, as well as any changes you’ve made since last year.

This way, you can narrow down which issue is causing the issue. 

If you manage to figure out which issue is affecting your furnace, you can then either fix it yourself or call in someone to do it for you. We’ll let you know what the best course of action is for each scenario, so you don’t have to waste any time. 

The Furnace Needs A Minute to Heat Up

There are very few instant things in this world. Furnaces still need a couple of minutes to heat themselves up in order to blow out hot air to warm you up.

If you hear your furnace making noise when you turn it on, don’t worry about it. It’s just getting ready for its first blast. Wait a little longer, and it should be able to provide the warmth you need.

Generally, a furnace should take no longer than 15 minutes to warm up. A little patience will go a long way, and sometimes that’s all that is needed. If, however, your furnace (see also ‘How To Troubleshoot A Trane Furnace‘) does not start to blow out after 15 minutes, you might have a different problem on your hands.

Hopefully some waiting around is all that is needed, and your issue will be solved.

The Furnace System Has Overheated

If you suddenly notice that your furnace is blowing cold air, it could be because the system has simply overheated. We say “simply”, but there could be three main reasons for this. We’ll take a look at these possibilities below:

The Furnace Is Old

Furnaces can last a long time, especially if they’re well-maintained, but sometimes things happen. The most common cause of a furnace failing is age.

If your furnace hasn’t been serviced or maintained in years, then it might not be working as efficiently as it once did.

This means your heater won’t be able to work as hard, which means that the temperature will fall faster than normal. In other words, your furnace will seem like it’s running slower than usual.

That doesn’t mean it’s broken – although it probably is. Just make sure you schedule service on your furnace soon! You might even want to get a new furnace altogether. Nothing lasts forever, and sometimes a new furnace is the best course of action.

Dirt Inside The Unit

It’s common for dirt and debris to build up inside the unit itself. When this happens, it can malfunction and stop working. You must clean out the filter regularly to ensure that your furnace runs efficiently.

If you notice that your furnace looks dirty, call in a professional to get it cleaned safely.

Not only would it take you a lot of time to clean the device thoroughly, but it’s easy to cause damage to it or yourself while doing so. 

The Furnace Isn’t Working At All

Finally, the third reason why your furnace may be blowing cold air is that it isn’t working at all. There could be a number of different issues going on here, so it’s best to have a licensed HVAC technician inspect it for you.

However, if you find that your furnace is indeed dead, you should start looking for a new one to get installed. 

Wrong Setting on the Thermostat

While some homes have thermostats that are set automatically to maintain a certain temperature, many others use manual settings. If yours is one of those, then you need to adjust it manually before calling an HVAC contractor.

Set the dial to the correct setting for the current weather conditions, and you’ll see a significant difference when you turn the heat back up later.

The thermostat is the single most important part of your heating system. Make sure you keep it checked regularly so that you know exactly how hot or cool your home is getting.

It’s so easy to forget to alter the thermostat settings as the seasons change, but this mistake can lead to you either being too hot or too cold in an instant.

If you notice that your furnace is blowing out cold air when it should be hot, just double-check your thermostat settings. This is one of the most common issues that people experience, and it’s an easy fix!

If your thermostat is on the wrong setting, just change it to the right one, and your problem should be solved. If the thermostat is on the correct setting, you can keep troubleshooting. 

To make life easier, make sure that the thermostat switch setting is on “auto”. If you leave the furnace on the “on” setting, the device’s fan will continue to blow air, even if the device has been turned off.

When this happens, it can lead to a couple of issues. By leaving the unit on the “auto” setting, you will be protecting the machine’s system. When it is on this setting, the furnace will turn on at the same time that the fan goes on.

Doing this is the most eco-friendly option, so you’re helping yourself and everyone else. 

There Could Be Bad Filters

There Could Be Bad Filters

Another possibility is that your filters aren’t doing their job properly. Unfortunately, the first place most people think to check is inside their house. They think it’s impossible for something outside to affect them, but that’s not always true.

One way that bad filters can mess up your furnace is by allowing dust into your home. Dust particles can enter through cracks around windows and doors, or even through vents. Once inside, they can clog the filter itself, causing any problems to begin all over again. 

The best course of action would be to call in a professional to get the job done if there are bad filters in the unit. They will get the job done in no time, and you won’t have to deal with the issue any longer than you need to.

A Dirty Filter Can Cause Problems Too

Even though filters serve an essential purpose, they don’t always do the job correctly. It’s possible for dirty filters to prevent the right amount of airflow. Therefore, they can actually reduce the effectiveness of your heater, forcing it to run harder than necessary. 

You can try cleaning the air filters yourself, or call in a professional to do it for you. A pro will know what they are doing, but it should be possible for you to do yourself if you really want to. It might take some time, though.

There Are Leaky Air Ducts

Air ducts also play a large role in keeping your home comfortable. They allow warm air from your furnace to circulate through the entire structure. If there’s a leaky air duct, this could cause the furnace to work harder than needed.

A professional service provider can easily spot these leaks, and they’ll take care of fixing them immediately.

Leaky air ducts result in the hot air escaping in places where it shouldn’t. When this happens, you won’t feel the heat coming from the furnace because it’s escaping out somewhere else.

There are many ways that air ducts can leak. Some may have split seams, while others might have loose connections. In some cases, air ducts can become damaged due to normal wear and tear.

Regardless of the cause, this condition needs to be addressed quickly before it gets worse. Don’t wait until you’re freezing to fix this issue, because it can cost you more money than you want to spend.

Get someone to come out and fix the problem as soon as you can.

The Condensate Line is Clogged

In a furnace, the condensate line is what connects the return side of the cooling coil with the drain pan. This is where excess moisture collects after the water evaporates. While it sounds simple enough, sometimes the condensate line becomes blocked.

The issue occurs when it rains, and the rainwater causes the lines to fill with debris. As soon as it starts raining, stop what you are doing and call a company like ours right away! We’ll come out to examine the situation, and we’ll get rid of the blockage in no time

There’s no Pilot Light on Your Furnace

The pilot light is located at the bottom of the burner assembly. In addition to heating your home, it serves another critical function: providing fuel to keep your furnace running smoothly. Without a working pilot light, your furnace will shut down automatically.

So, if you notice it has gone out, make sure to turn off your power, open the door to the furnace, and try relighting it.

In rare circumstances, it could mean that your gas valve isn’t working properly. Make sure to contact a good gas technician, but remember to never use a match or lighter to relight the flame. Doing so can create a fire hazard!

Your Furnace Isn’t Making Enough Heat

This last point goes hand in hand with the previous one. If your furnace isn’t producing enough heat, then it won’t stay warm throughout the winter months. This means that you will have to keep adding wood to your fireplace during cold weather.

But if you do this, then you run the risk of catching yourself up in an endless cycle. You can avoid this by installing a programmable thermostat (see also ‘Best HomeKit Thermostats’). With one, you’ll only need to adjust the temperature settings when you’re home, and not all day long.

There’s Another Thermostat Issue

There are a number of other thermostat (see also ‘No Power To Thermostat? | Try These Troubleshooting Tips‘) issues that could be to blame for your furnace issues. One example is fault wiring. It’s possible that there’s something wrong with the wires going into your unit.

You may also be using a thermostat that is not compatible with the unit and heating system that you are using. 

It might take some deduction, but if you think that you may be suffering from a thermostat issue, don’t hesitate to call in the pros. Thermostats can be hard to work with, and if you don’t know a lot about them, you could waste a lot of your time.

In any case, don’t hesitate to call us professionals about your problems. We’d love to help you out!

Your Furnace Needs Maintenance

It may seem like a simple thing to change the air filter, but it’s actually quite dangerous in the long term. Every year, homeowners should clean or replace their filters. These filters are specifically designed to remove impurities from the air.

If they become clogged, they won’t perform their function well enough. In addition, changing the filter every year helps ensure that you get the best performance from your HVAC system.

In addition, make sure that your furnace isn’t making loud noises whenever you turn it on or off. That’s another sign that the pilot light could be malfunctioning.

Finally, you should check your owner’s manual to see what type of flame sensor is used in your system. If yours has been replaced recently, then it was likely installed incorrectly. Fortunately, this is something that our team can repair without any hassle.

Final Thoughts

A malfunctioning furnace is not fun to deal with, especially in the winter. Thankfully, the majority of possible issues can be quickly dealt with. If you would like someone to take a look at your furnace, give us a call.

Whether it’s a full furnace repair, or simple checking on a dirty air filter, we can get the job done.

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By Anthony Barnes

Anthony Barnes is the founder of Water Heater Hub and a second-generation plumber by profession. Before developing Water Heater Hub, Anthony Barnes was a full-time plumber, and he has undertaken a wide variety of projects over the decades. As a second-generation plumber, it was easy for Anthony to get used to the technicalities of all from a tender age