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Why Is My Heater Not Blowing Out Hot Air

Get Quick Air
30 Jul 2019
3 Min Read

The importance of heating your home during winter/cold weather cannot be overemphasized. However, like any other electrical/mechanical machine, heaters experience technical problems that hinder their normal operations. One common problem with heaters is blowing cold air instead of hot air. The problem can be very annoying, especially when you want to warm up your interiors. Do not panic because this article will enlighten you on why your heater is not blowing out hot air. Even more, you will learn about what to do to correct the problem.

How Heaters Operate
Heaters are designed with highly conductive coils called heat exchangers. These coils are heated using electricity, natural gas, oil, or any other heating substance. Besides the coils, heaters have a fan (blower motor) which blows cold air over the heated coils. As the cold air passes over the hot coils, it gathers heat energy. The hot air is then pushed into the ductwork of your house by the blower motor. The process is repeated until your home attains your preferred temperature.

Why Your Heater May Fail To Blow Out Hot Air

1. An Incorrectly Set Thermostat
As easy as it may sound, a thermostat that is not set to the correct mode will affect the heating operations of your heater. When your thermostat mode is set to ON, for instance, the blower motor will run continuously even when the air passing over the coil is not heated. In this case, set the thermostat mode to AUTO to ensure that the fan only runs when the air passing over the coils is heated.

2. Broken and Leaking Ducts
Undoubtedly, several reasons can render your ductwork ineffective. Aging and lack of proper maintenance services can significantly deteriorate your piping system. When your heater blows out hot air, the air mixes with the cold air that penetrates the ductwork from the outside. The resultant effect is a cancellation effect that cools down the hot air from the heater. Consequently, you will feel as if your heater is blowing out cold air. Contacting a heater service professional to service your ductwork will help in restoring the efficiency of your heating system.

3. Dirty and Clogged Air Filters
A dirty air filter reduces the efficiency at which air flows over the heat exchanger of the furnace. As a result, the heat exchanger becomes excessively hot and shuts down automatically to prevent thermal damages. In effect, cold air is pushed through the pipes by the fan causing your heater to blow out cold air. To correct the problem, you can clean the air filters or hire a heater service technician to do the cleaning for you.

4. Improperly-Sized Heater
The size of your heater plays a pivotal role in determining the effectiveness of the heater in performing its intended functions. A furnace that is smaller than the heating demands of your home will not distribute hot air effectively to all the rooms of your house. On the other hand, a larger furnace will continuously cycle between ON and OFF, consuming excess heat energy. Contacting a heater repair professional to replace your heater with the correct heater size will rectify the heating problem.

5. Dirty Flame Detector/Sensor
A flame sensor that is covered with dirt and soot will not function effectively. A dirty flame sensor causes your heater to cycle between ON and OFF. Repeated ON-OFF cycles will not provide your heat exchanger ample time to heat up adequately. Consequently, the furnace will not heat your house effectively. The overall effect that you will experience will be as if your heater is blowing out cold air. Cleaning the flame sensor will go a long way in diagnosing this problem.


As seen above, different reasons can make your heater fail to blow out hot air. These reasons include an incorrect thermostat setting, broken ductwork, dirty air filters, wrong-sized heater units, and dirty flame sensors. Also, the recommendations suggested above will help in ensuring that correct measures are taken to troubleshoot the above heater problems when they occur. If you are unsure where to start, then please feel free to contact us on 1300 730 896 and we will arrange a technician to look after the heater for you. Quick Air provides same day service Australia wide.