• The job of your furnace is to keep you and your home warm by heating up the air with a flame and then circulating it around your property. When this works well, it is very useful for surviving the colder months and basic heating is something that no home should be without. So when it starts blowing cold air you have a problem. When you find that your furnace is responsible for the sudden drop in temperature, it can feel like something of a betrayal. But fear not, as once you’ve found the cause there will often be a simple solution…

    Let’s address some of the most common issues…

    Thermostat Settings

    The thermostat settings can sometimes be the problem and this might lead to a simple fix.

    If your thermostat is set to ‘On’, then this means that the blower is going to run continuously. That means that even when the furnace isn’t heating the air, the air is still being blown and can like cold air! Instead, you should set your thermostat to ‘Auto’ which means the blower will come on automatically when it is needed and not the rest of the time. Now you should find that the furnace only blows warm air while it is running. If not some other issues are described below.


    If things get too hot, then they can get a little cool. Ironically.

    Basically, your furnace can overheat. Often due to a dirty filter, defective blower motor or capacitor which starts the motor. If there is little to no air flow moving across the furnaces heat exchanger it will cause a high temperature limit switch to turn the burners off as a safety measure. Before scheduling a furnace repair appointment be sure to check your return air filter, ensure it is not so dirty that it is causing an air restriction to the system. If the system will not run you may also want to try removing power from the furnace via the disconnect or circuit breaker for 30 seconds and restoring power. In the case of 3 consecutive limit switch trips the system will lockout and not allow it to run until it has been reset by removing power.

    Pilot Light is Out

    Another tip is to check the pilot light (on older furnaces, newer models are electronic ignition). If you have a pilot try relighting it if extinguished, in some cases that simple step will be the only problem. If it won’t light though, then you need to make sure that the gas supply is working correctly. If it lights and won’t stay lit then it is time to schedule an appointment with a local HVAC company. There are plenty of other issues which can stop cause a furnace to stop heating properly or all together, these are the most common issues that can be DIY repaired with a little research.