What Are the Most Common Furnace Problems?

Arlington, Texas – During the cold winter months, most homeowners count on their furnaces to keep them warm. Your home’s heating system keeps the indoor temperatures at a comfortable, toasty level. Whereas, most furnaces are designed to last a very long time, eventually, things can and will go wrong. Most of the time the problems are relatively easy to fix. Oftentimes, the catalyst for the problems is due to lack of furnace maintenance.

Whenever a problem arises, a professional technician will be able to take care of the issue quickly. However, sometimes a homeowner may be able to fix the problem themselves. Below we go over some of the most common furnace problems. Some, a homeowner can easily take care of themselves. Whereas others will most definitely require the service from a professional heating and air company.

Lack of Furnace Maintenance

Starting off at the top of the list is the lack of furnace maintenance. Surprisingly, most homeowners do not keep maintenance up to date with their heating and cooling systems. This is surprising because next to the home and vehicles, an HVAC system is usually the third most expensive object in a homeowner’s possession. Most people make sure to have the oil changed when their vehicles need it. The same is said about tune-ups and keeping the home in tip-top shape.

However, when it comes to heating and cooling, homeowners tend to wait until something goes wrong. A furnace is composed of many internal parts just like a home and a car. If neglected, those parts will break down. However, when maintained, you get the most out of your investment. The same can be said with your home’s heating, ventilation, and air conditioning.

Frequent furnace maintenance will ensure that your heating runs efficiently. It will decrease the possibility of major breakdowns. Additionally, keeping it maintained will even save you money with energy costs. The cost of maintenance pales in comparison to the costs associated with not having it maintained over the long run. A poorly maintained furnace may last 3 – 5 years, whereas a frequently maintained one could last more than a decade. You do the math.

The Furnace is not Producing Heat

A furnace has a singular purpose. What is that purpose?  The purpose is to generate and distribute warm air throughout a home. Whenever your heating stops producing heat, you may instantly assume the worse. However, in most cases, it is usually something minor. Let’s explore what the reason could be behind this.

Incorrect setting on the Thermostat

  1. The temperature may be set to low
  2. Is the thermostat set on Fan mode?
  3. Perhaps, the thermostat is turned off?
  4. The thermostat is not set to heat mode.

One of the first things you should check if your furnace is not producing heat is the thermostat. Rule out all the above before moving on to the next part. If you determine that the thermostat is not the problem, then you should check for the next possible cause.

Furnace Air Filter

The purpose of the furnace’s air filter is to prevent dust, debris, and other particulates from entering the ductwork.  Without an air filter, the dust and debris would be blown throughout the home. This not only would make a mess, but it would also aggravate allergies and possibly make someone sick.

Most furnace manufacturers state to replace the filters regularly. Some manufacturers may even require that the filters be replaced on a certain time basis to maintain the warranty. Depending on how often you use the furnace will determine how often you will need to replace the filter. It could be anywhere between once every winter season to as often as every month if not more.

If you have a large family and/or pets you will most likely need to exchange the air filter monthly. If there is someone in the home with a compromised immune system or respiratory problems, it could bi-weekly.

When the furnace’s air filter becomes clogged with dust and debris this will prevent airflow. This could possibly make it seem as if the furnace is not generating any heat at all if it is restricted. On top of this the furnace will work overtime trying to heat the home. This will eventually cause the furnace to prematurely fail.

If the air filter was recently replaced or is not dirty, then move on to the next step to ascertain why the furnace is not producing heat.

Check the Breaker Box

If you have an electrical furnace, then you should next go to the breaker box. Once there check and see if the breaker for the furnace has flipped off. If so, flip it back on and then check and see if this resolves the issue. If so, great. However, there possibly could be something else going wrong for the breaker to flip off. You should seriously consider scheduling professional service with a local heating and air service company to inspect the heating system. However, if the breaker is on then move on to the last step.

The Furnace’s Ignition or Pilot

If you have already inspected the above, then the problem could be the ignition switch or pilot light. The purpose of the pilot light is to ignite the fuel for the furnace. If you have an older furnace, then the pilot light may be constantly lit. If so, there is a chance that the flame went out and you will need to relight the flame. However, if you have a fairly recent furnace then it most likely will have an electronic ignition. An electronic ignition switch ignites the pilot light whenever the furnace cycles on. If the electronic ignition is not igniting a flame, then the switch may be bad and will need to be replaced.

At this point in troubleshooting if none of the above worked you will need to get in touch with a professional heating repair company. The next steps will mean working directly with fuel or electricity and that is much too dangerous for someone who is not professionally trained in either.

The Furnace keeps Turning On and Off

Another common problem that can arise with furnaces involves them continuously turning on and off.  Professionally speaking, we call this cycling.  Whenever a furnace heats your home, it will cycle on to do so. Once the indoor temperatures have been met by the settings on your thermostat it will cycle off. This is normal, and how it should operate when all is well.

However, if the furnace cycles frequently before it even reaches the set temperature on the thermostat, then there’s an issue. When this happens, it is referred to as short cycling. One of the most frequent reasons behind a short cycle is lack of airflow. The lack of airflow will cause the furnace to overheat. When this happens, a safety switch will shut down the heating to prevent catastrophic failure or worse.

You may think that whenever the furnace is short cycling it is most likely a big problem. The problem itself is quite serious. However, the reason behind it is usually something very minor.

Clogged Air Filters

A clogged air filter is the most common reason why a furnace will short cycle.  If you are having this problem the first thing you should do is check the air filter. Then, if the air filter is clogged and/or dirty, then replace it. Finally, if this resolves the issue, great.  However, if it does not then it, unfortunately, will be a more complicated matter. You will need to get in touch with a professional heating service company to inspect the system.

The Furnace is making too Much Noise

No furnace is completely silent. There will always be some noises coming from them when they are in operation. However, if you hear noises from the furnace that you usually do not hear, then this could propose a problem.

Do you hear a knocking or rattling noise coming from the furnace? If so, then an inner part possibly could have become loose and will need to be reaffixed.

Do you hear a loud rumbling sound? This could be possibly due to fuel being left within the combustion chamber whenever the heating cycles off.

If you hear any of these noises, you should immediately shut off the furnace. After you have turned it off, call a professional heating repair company to inspect the system.

The Furnace is not Heating Enough

If your furnace turns on and is generating heat but not enough there are multiple reasons this could be happening. Below we go over five of the top reasons this could happen.

The Ductwork is the Problem

If you have always experienced this problem in the home, then quite possibly the ductwork layout itself is bad. However, if it is a more recent problem, it could be due to the following:

  1. Animals – Rodents or other pests may have infiltrated the ductwork. They could have built a nest inside the ducting blocking airflow. Another possibility is they have punctured the ductwork allowing too much air to escape or dislodged it.
  2. Loose Ducting – The ductwork may have become loose and the conditioned air is leaking out of the enclosed system.

Issues with Ventilation

Another common problem behind insufficient heating is due to bad ventilation. Furniture may be obstructing the airflow from vents in some of the rooms. However, the most common problem is usually with the air filter. If the air filter is not frequently changed it will build up with dirt and debris. Once it is clogged then heat will not be distributed efficiently.

The Furnace is Short Cycling

This was already explained above when a furnace continually turns on and off. As explained above it is most likely due to a clogged air filter. However, there are multiple causes as to why this can occur. Additionally, the most important factor in short-cycling is the fact it puts excessive strain on the system.  This will lead to larger problems that cost much more.

Problems with the Thermostat

The thermostat could be malfunctioning. On the other hand, it could also be miscalibrated. Finally, it is also possible that the connection between the furnace and the thermostat is disconnected. Chances are a professional technician will need to have a look at this and address it for you.

The Furnace is rather Old

If the above issues turn out to not be the problem, then the furnace is probably too old. One of the tell-tale signs of an old furnace is uneven heating. This is a warning that the heating is nearing the end of its service life. Just like the embers in a dying campfire, so to will a furnace’s ability to generate heat fade. If your furnace is more than 10 – 15 years old, you will need to have a professional technician inspect the system. They will be able to determine if there is more life in the system or if you are better off purchasing a new furnace.

There’s Water coming from the Furnace

As odd as this sounds, there are some types of furnaces that can develop water leaks. These water leaks are due to condensation. If you are the lucky owner of one of these furnaces, then you have what is called a high-efficiency furnace.  Furnaces such as this will have an AFUE rating of over 90%. One of the features in most high-efficiency furnaces is referred to as cool exhaust. These furnaces will usually have PVC exhaust pipes instead of metal pipes. Additionally, they will have condensation pipes.  The condensation pipes will direct the water to a drain. If the pipe becomes obstructed, then you will notice water around the furnace. If you see this, then you will need professional help from a heating repair company.

Furnace Fan is Continuously Running

Have you found yourself in a situation where your furnace fan is constantly running? Then, the first thing you will want to do is check whether the thermostat is set to AUTO not ON. Next, turn the thermostat to a lower temperature than the current temperature in the room. If the furnace fan is still running after three or four minutes, then that proposes a problem. Usually, whenever this happens it is due to three problems. Those problems are listed below.

Fan Limit Switch

The first problem is that the fan limit switch for your furnace may be set to MANUAL OVERRIDE. To fix this, you will need to find it if you do not already know where it is. Go to your furnace and find the panel cover. The panel cover is usually located near the upper right corner of the system.

The fan limit switch’s responsibility is to turn the fan on and off at the correct times. If it is operating correctly, it will switch the fan on when heat is needed, and when the set temperatures are met it will shut off the fan. However, if this is not happening then the switch is set to MANUAL OVERRIDE or has become faulty.

Locate the fan limit switch in the panel box. It is usually a small white button located in the lower-left corner of the panel box. If the button is pressed in, then it is set to MANUAL OVERRIDE. This would be the reasoning behind why the fan is running continuously. Press the button to reset it to AUTO. If this fixes the issue, then great. However, if the problem persists then you will need professional assistance.

This leads us to the second problem, a faulty fan limit switch. Which as stated above if resetting the switch does not rectify the situation then this is the possible problem. However, there is also a third possible problem. The third being, a problem with the electrical wiring between the thermostat and the heating system.  Either way, both problems require professional help.

This leads us to the final most common problem with a furnace and an obvious one at that.

Wear and Tear

Is the furnace more than a decade old?  If so, it is possibly nearing the end of its service life and will need to be replaced. However, if it is not that old, then it may have possibly been neglected over the years. If air filters are not exchanged often and the heating is not maintained, then the service life will decrease. Therefore, we cannot stress enough that it is vital that your furnace receives professional maintenance. We suggest that at a minimum you receive furnace maintenance at least once a year.

Are you are experiencing problems with your home’s furnace? If so, and you need professional heating repair do not hesitate to give Metro Express Service a call. You can reach us at 817-476-7652 or 972-263-2500. We are one of the leading heating and air service companies throughout the DFW area. Family-owned and operated for over twenty years, you can count on us twenty-four hours a day, seven days a week. When you hire MES for your HVAC needs you can rest assured knowing you made the right choice.


Randy Murphy

Randy Murphy has been building his knowledge of the air conditioning and heating business for several years now. He first started applying his knowledge while working for his father’s HVAC company. Later, in 1987, Randy started his own business: Metro Express Service. He has been a top 10 Trane & Amana dealer for over eight years. When it comes to heating and cooling, Randy knows the business better than anyone.
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