Furnace blowing cold air


Here in the New York City area, we’re all pretty tired of the cold weather by now. No matter how you travel to work, whether it’s by bus, car or train, your commute probably ends with a cold walk in the icy January wind. When you get to your destination, you expect to walk into a toasty warm building. The last thing you want to find is that the furnace is not working. Even worse, it’s actually blowing cold air!

Even if your furnace is fairly new, things can go wrong that cause this unpleasant surprise. In some cases, you may be able to fix the problem yourself. But you need to know when to call in the furnace repair pros so you don’t have to spend unnecessary time in the cold and interrupt your business. You also don’t want to risk frozen pipes.

Read on for the 13 most common reasons that your furnace may be blowing cold.

1. Incorrect thermostat setting.

Do you have thermostat wars going on in your office? If so, someone may have been too hot yesterday,...

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You might think that a heater blowing cold air is not a common problem for a Santa Clarita heater repair company, but this one was emailed to us by Jeff over in Redlands where it can get quite chilly in the evenings, especially in the winter. As I’ve said before, most of the topics we discuss come from questions we are often asked but I like this one in particular because we got an email about it. Regardless of whether you are in the Santa Clarita area or in Michigan, knowing how your heater works and what problems it may have is the key to figuring out why you have a heater blowing cold air. I know that heat is not usually a priority in Southern California, but if you live in the San Bernardino mountains then a heater blowing cold air can be pretty concerning when the temperature starts to drop. Those of you who read our articles regularly, know that we are a small, U.S. Veteran-Owned HVAC company in Southern California, and pride ourselves in giving people honest, straight...

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If your furnace is blowing cold air, we’re sorry! It’s a chilly problem that no one should have to deal with during winter in the Atlanta area!

There are several possible causes for a furnace blowing cold air, so it’s hard to give you advice without more information.

But here are 3 common causes you can fix yourself.

1) Thermostat is set to ON
Is your furnace blowing cold air only sometimes? Is the furnace’s blower constantly running?

Check your thermostat. (That’s where a tech will start first, so you should as well.) If your thermostat’s fan setting is set to ON, the furnace blower will constantly run even when your furnace isn’t heating the air.

Solution: Turn your thermostat’s fan setting to AUTO. Now your furnace will only blow warm air.

2) Furnace overheated
Let’s say your furnace blows hot air, then cold air, but then stops blowing any air at all after a while. What’s the problem?

It’s possible your furnace...

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If your furnace is blowing cold air when it is turned on and the thermostat is set, there are a few possible reasons why. In some cases, you can resolve the issue yourself, but in others you really should call a maintenance company.

However, in order to know what the cause of the problem is, you need to eliminate the most common problem makers. And if the problem is too complicated for you to resolve yourself, make sure that you contact the right company to do the job, like https://www.actionac.net/heating-repair-san-diego-ca.

Chip Glitch

The first thing you can do is the simplest. Check whether your furnace is on. Most newer furnaces have a computer onboard in order to ensure that everything is in working order. However, sometimes this computer is the cause of the problem. It can sometimes start the fans without releasing the fuel supply, causing the cold run.

Resolving that problem is really easy. All you need to do is...

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When the chilly weather finally arrives and you have to turn on your furnace for the first time after many months of non-use, the last thing you want to find is that it’s not working.

Or, even worse, you discover that it’s actually blowing cold air! It can be incredibly frustrating to have to deal with a malfunctioning furnace right when you need it the most.

Still, there’s no reason to panic.

As exasperating as this situation may be, the solution may be a simple fix.

What follows are five of the most common reasons a furnace may blow cold air.

With most of these situations, you can probably correct the problems yourself. In other instances, though, you’ll need to call for help from an HVAC professional.

The Furnace Hasn’t Warmed Up

If you get a blast of cool air when you first turn on the furnace, but after a couple minutes the air feels warm, that is nothing to be concerned about. It’s normal for cool air to emerge from...

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I am no expert on gas furnaces by any stretch, but have had similar problems with units over the years in rental properties. I often shadow my heating subcontractor because I am always curious to learn how these things work and pick up tips. I'm sure there is a control panel or control board that monitors gas flow in, ignition, fan functions etc. This logic control is designed to shut the supply of gas if ignition fails after a predetermined period of time. I can't tell you how to test the specific control board, but I would bet the problem is one of a few things. Bad igniter, faulty gas control valve, or control board failure. I know this is very vague and not really helpful. If you have spare parts, you could try the simple substitution routine. I'd start with the igniter, then the controller, last the gas feed. If you need heat now and fast, this might be a situation to call a tech, get it fixed fast and learn from the tech for the next time you have a...

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Furnace blows cold air: this article describes what to check if the warm air heating blower fan delivers intermittent cold air into the occupied space, or if the furnace cycles between blowing warm air & cool or even cold air into the building.

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How to Diagnose & Fix a Blower Fan that Blows Alternating Hot then Cold Air

Question: forced air heating furnace blows COLD, HOT, COLD, then OFF - what's up with its fan limit control?

Fan Limit Switch Problem History

Two story 75 year old classic cape cod home. Gas forced air furnace is Lennox G16 24 years old, in good condition. With Honeywell fan limit switch, outside fresh air intake and draft motor. We have owned home 12 years. (has AC). Owner not a technician but...

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Is Your Furnace Blowing Cold Air?

Your furnace might be running just fine, but the air blowing out of your vents feels cold. When it is chilly, having a heater that is not working is a major cause of concern. though several reasons can cause this problem, there are a few things you can do before you call a professional. Here is a guideline to help you troubleshoot and possibly solve the issue.

Check the thermostat

The air coming out of your vents might seem rather cool or your home is not staying as warm as the temperature you set. Maybe your heater is not blowing hot air even though the fan is running. As a result, any air that blows out of the vents while your heater is off will usually feel cold. In such a case, there could be an easy solution, particularly if your thermostat setting is the problem. Regardless of whether the unit is heating the air or not, the fan on a heater will keep on blowing as long as the thermostat is set to ON.


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Why is Furnace blowing cold air?

The central air heater provides a feeling of comfort inside the room and keeps the inhabitants away from the illnesses related to cold at the time of summer. The quality of life can be increased in the presence of air heater. There are few types of furnaces that can produce heat. They are oil fired forced hot air furnace, forced air electric furnace and gas fired forced hot air furnace. These furnaces give out heat to keep the room warm. But at times when they are under repair, they give rise to cold air.

The furnace is said to provide heat to the entire house in some calculated quantities depending on the house size. The features that are the cause for safety, makes the furnace to manage the temperatures at desired levels. But, these safety procedures may not function properly sometimes. This makes the furnace to blow cold air.

In the case of gas fired furnace the heat is generated when the burning of gas and maintenance of the...

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The winter is upon us and there’s nothing worse than wanting to heat up your home but you’ve got a furnace blowing cold air instead of warm air. There are several reasons why this could happen. Here are the three most common reasons why your furnace can be blowing cold air.


The first step you should take if you are feeling cool air in your home is to check the thermostat. If you have the fan set to “ON” rather than “AUTO” this means that the fan will be running constantly. When the heater is not running the fan will blow cool air. If you set your thermostat fan to “AUTO” then it will only blow warm air when needed.

Another issue with your thermostat is that it could possibly be set to “COOL” rather than “HEAT”. If that is the case, switch it to heat and wait a few minutes and it should start blowing warm air.


If your furnace is blowing hot air and then cold air and then it stops altogether you may be wondering what the...

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A furnace blowing cold air would making any homeowner hot in the face. It’s annoying, right?

Troubleshooting this issue depend on how exactly the furnace is blowing cold air:

Does your furnace blow warm air sometimes and cold air other times? Read the first section of this article.Does your furnace always blow cold air? Read the second section.

A furnace that blows warm air sometimes but cold air other times is usually caused by one of 2 things: either you have your thermostat fan set to ON or your furnace is overheating.

Problem: Thermostat set to ON
The fan in your furnace blows the heated air through the vents in your home. If set to ON, the fan will continue to blow air, even when the furnace isn’t actually heating.

This can make it seem like the furnace is blowing cold air, though it’s really just blowing room-temperature air.

Try this: Next time you feel cold air, check the thermostat to see if your home’s temperature has reached your...

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Is your furnace blowing cold air, or maybe it is having problems keeping your house warm.

People are more likely to notice issues with their furnace as temperatures begin to drop and we transition from air conditioning to heating. It might be running just fine when you suddenly realize that the air is not warm. As a matter of fact, the air might be downright cold.

For most of us, the question remains; why is my central heater not blowing hot air? You are probably wondering what the problem is and whether you should be alarmed.

A heater that is blowing cold air can be a cause for concern, particularly on a chilly day.

Since several possible reasons can cause it to blow cold air, it’s hard to give advice without additional information, which is why we will share what we know about this issue. You might be able to complete some of the repair work, but if the scenario is a little bit more technical, you should contact a professional HVAC company to diagnose...

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The last thing a Lake Zurich, IL homeowner wants in winter is a furnace that’s blowing cold air. Why would a furnace do that? Well, there are three common reasons. The good news is that you can probably fix these problems all by yourself.

The Thermostat Is Set To “On”

When the thermostat is in the “On” position, the blower will continue to blow air whether that air has been heated or not. To rectify the problem, simply set the thermostat to “Auto.” With this setting, your heater will blow warm air only.

Your Furnace Has Gotten Too Hot

If your furnace has overheated, it was previously blowing hot air just like it should. But then it started blowing cold air, and after that, it blew no air at all. The most likely scenario is that your heating system got too hot. When that happened, something called the limit switch shut down the burners. This is a heating safety device designed to prevent overheating. When the burners are off, the blower blows cold air...

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Is your furnace running but the air that’s blowing out of your vents seems cold?

There are a couple things you can do to troubleshoot the problem before calling a heating repair company.

Check the thermostat

You might have walked by a vent and noticed the air seemed cool. But is your home staying warm, at the temperature you set it at? If it is, the problem might be a simple thermostat setting.

Check your thermostat and make sure that it is set to “auto” rather than “on.” When set to “on”, the fan on your furnace will blow continually, even when the furnace isn’t actually heating the air.

So if you feel the air blowing out of the vents while the furnace is off, the air will seem cool since it’ll be at about room temperature.

Change the air filter

A dirty air filter restricts airflow into your furnace. Restricted airflow can overheat your furnace, causing a safety control to shut off the burners.

This safety mechanism...

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Is your furnace blowing cold air?

If your furnace is blowing cold air, we have tips to share with you! Even being in southeastern North Carolina, it can get chilly during winter months (especially at night). So if your furnace is blowing cold air–getting is resolved can greatly improve your comfort.

There are numerous possible causes for a furnace blowing cold air, so it’s often recommended to consult a certified HVAC contractor. Some common causes that you can fix yourself include; thermostat settings, the pilot light being out, furnace overheating, and dirty air filters.

First things first, check your thermoset.

Is the fan set to “on”? If not, turn your thermostat’s fan setting to “auto”. Now your furnace should blow warm again.

Is the pilot light out?

If you have a gas furnace and the pilot light is out, it often causes the furnace to blow only cold air. You can try relighting it. If the problem continues, check the gas valve to...

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You don’t have to be an HVAC expert to know you have a problem when your furnace is blowing cold air. But, before you start reaching for your wallet and stressing out about major repairs or replacement, consider these five furnace troubleshooting tips. They could save you time and money and turn a catastrophe into a minor inconvenience.

1. Check your thermostat. It sounds too easy, but this is often the problem when the furnace is blowing cold air. Your unit must be set to heat to warm up your home. New “smart” thermostats often have a steep learning curve to operate, but once you are up to speed they are remarkably efficient in saving you money on energy costs.

2. Change the filter. Another easy fix but it is important and often overlooked. Furnaces utilize filters to clean your air and keep dust and debris out of the system. When the filter is clogged the furnace must work much harder to produce the same results. Many furnaces will shut off instead of continuing to...

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In the cold weather, it is important to have warm air in the house. Occasionally problems may develop with your heat system. You may notice your Lennox furnace blowing cold air. You will want to investigate what is happening and why.

Checking the burner

Observe your unit as it kicks on. Is the burner lighting? If so, there are other things to look for. Here are a few suggestions.

Blower speed

There can be a lot of different things that will affect the heat. Try to think of the simplest solutions first. Is it early in the season? You probably have a central air unit that uses the same blower motor.

Most blower motors have speed control settings. In the summer, you want to have the blower on high mode. This will give you maximum cooling capacity.

In the winter, the blower should be set for a lower speed. This will make the air warmer. If it is too high, the air may feel cool or not as warm. Check to see if the blower is set on...

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Our house was built in 1968. Yesterday a furnace guy was out to do a general checkup. He pointed at that we have:

1) Normal cold air return from all throughout the house
2) Cold air intake from outside piped directly in to the furnace
3) Makeup air vent in furnace room

He basically said #2, the cold air from outside directly in to the furnace, was "what they did 40 years ago" and was basically killing our furnace efficiency, since on the coldest days it was pulling in and having to heat outside air, possibly down to 10 below on our lowest days.

I'm inclined to believe him, however I also just wanted to get a second opinion before removing it and letting the furnace run on only return air from the house and the makeup air vent. Anyone know what the actual "code" is on that or where I can look to find...

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Posted by Satyendra on Apr 29, 2015 in Technical | 0 comments

The Process of Blowing-in of a Blast Furnace

The process of starting a blast furnace after its construction or after its relining is called blowing-in. The blowing-in process is carried out in several steps (Fig 1) which consist of (i) drying out the lining, (ii) filling of the blast furnace with a specially arranged high coke blow-in furnace charge, (iii) igniting of the coke or lighting of the blast furnace, and (iv) gradually increasing the hot blast (wind rate) with frequent castings to ensure the raising of temperature of the blast furnace hearth. During the period of blow-in, the burden ratio (ratio of the ore to coke) is adjusted according to a predetermined schedule until the normal operation of the blast furnace is achieved and the blast furnace starts producing the normal quality of the hot metal.

Fig 1 Steps in the blowing-in process of a blast furnace

Newly constructed...

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