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The number one reason that can cause your furnace to stop working (believe it or not) is a dirty flame sensor! If your furnace is turning on for a few seconds and then stops working, this is highly likely to be your problem.

A furnace is a traditional heating system that is used widely around the world in homes, offices, and industries. Previously operated by burning wood and coal, in today’s world, it is powered by oil, gas, or electricity.

During the chilly weather, a nice, warm furnace is part of “a survival kit” for people living in the northern parts of the world. A gas furnace is a much cheaper version of the furnace and more common among the Europeans.

You can also go with an electric furnace which is a better option if you can bear the costs and is environmentally friendly. In this article, I will go over the most common furnace problems (and solutions) of a gas furnace.

Here is a very detailed video on how to find the flame sensor inside the furnace and what is the best way to clean it:

Newer furnaces also have an ignition lockout feature. This means that after trying to ignite without success 5 times in a row, it will shut off the power and fuel for 3 hours. You can reset it by turning it OFF and ON again (3 secs).

Furnace basics

Knowing the basic functionality of a furnace can help you examine the issue much properly by looking at the right places and solve the occurred problems.

A furnace consists of 4 essential parts:

  • Thermostat. It gives a signal to the furnace for temperature changes.
  • Burner. As soon as the signal from the thermostat gets in, fuel is rushed to the burner for temperature rise.
  • Heat Exchanger. After the fuel starts to burn, the temperature rises resulting in heating up the heat exchanger. The heat exchanger keeps away all the hazardous fumes from coming through vents in a building.
  • Blower Motor. Heated air is sent to the heat exchanger by the blower motor and then distributed through vents throughout the building.

Troubleshooting furnace

It is devastating if all of a sudden your furnace stops delivering heat during chilly weather night! So, let’s start by looking into what could cause a furnace to stop working.

Before you start checking or touching anything inside the furnace, make sure that your power is OFF! It’s a good idea to leave furnace fixing to a professional because there is a lot of electricity and gas involved.

But if you want to know what could possibly go wrong with your furnace before your call for professional assistance, here is a very informative video on the top 5 problems with furnaces:


Most furnaces are smart enough to let you know what is the problem with them by blinking light! This means that before your start resetting your furnace, make sure that you write down the “light code” that your furnace is “telling you” about.

Here is a list of problems of what could possibly go wrong with your furnace (we will be talking about a gas furnace):

#1. Thermostat batteries

A furnace may stop working if the thermostat is not adjusted right or the batteries in it are weak and this causes the furnace to wear out. To avoid all the discomfort keep an eye to change batteries on time and set the thermostat accurately.

#2. Faulty heat exchanger

A ruptured heat exchanger may create issues in the heating process of the furnace due to constant heating and cooling. In an event of a cracked heat exchanger gases such as carbon monoxide might enter through the ducts.

This can be taken care of by a timely expert check-up of the furnace.

#3. Clogged or jammed filter

A dirty or jammed filter affects the efficiency of a furnace. It restricts the airflow and exhausts the furnace causing it to stop working. Changing filters can save you the damage and ensure the desired warm airflow.

#4. Dirty furnace ignition

The furnace ignites through a pilot light. An unclean pilot surface will not let the furnace ignite for too long and must be cleaned to be ignited for a longer period of time.

#5. Mechanical issues (check for noise)

A noisy furnace can be a sign of mechanical issues. Clogged filters, a loose part or a leak problem can give rise to noise problems in the furnace.

#6. Gas leakage (the very dangerous problem)

If the gas valve connected to the furnace is not turned on or a gas leakage occurs then this may cause the furnace to stop working. Gas Leakage must not be ignored and should be dealt with immediately.

#7. Is your furnace too old?

If problems in your furnace keep on occurring again, it’s time for a new furnace. Ask for professional help, to match the furnace requirements of your place where it has to be installed.

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Preventive maintenance

Maintenance of a furnace should be carried out annually by professional experts to eradicate malfunctions in a furnace that causes it to stop working. Keeping a furnace clean and taking care of the repairs prolongs its life.

Troubleshooting a furnace is not easy to do on your own, therefore if the problem does not look simple at all, make an appointment with a furnace specialist right away. And, of course, a pre-winter checkup on your furnace before it gets freezing cold outside is generally a good idea.

Attention! This article is for informational purposes ONLY and is NOT a replacement for a professional advice! You will need to visit school's website for details and updates, as well as consult your local HVAC specialist for appropriate solution to your problem.


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1 Comment

  1. Zachary Tomlinson

    I would never have thought that a faulty heater thermostat controller could cause temperature inefficiencies and affect your overall heating experience. My uncle wants to try moving to the mountains and he’s worried about how the winter season would hit him by then. This information can probably help him prevent furnace breakdowns in the future.

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