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Suppose you have turned your heater on only to find no hot air coming from the furnace. There are several reasons you have no hot air coming from the furnace. Below I’ll be going over the possible reasons for this problem, and because I wouldn’t say I like to leave you with no solutions, I’ll leave you with a few possible DIY fixes for a furnace that is not working correctly.
Read also: House heater not blowing hot air
Reasons You Have No Hot Air from Furnace
1) Thermostat Issues
The thermostat is the first thing you must rule out when you trouble shooting a furnace that is on but not blowing hot air. Many times, it turns out that a furnace doesn’t have a problem at all, but your thermostat does. So, make sure your thermostat does not have these issues below.
- Fan set to “on”: This is a common reason for your furnace not doing a proper job. Your furnace does not blow hot air continuously. Instead, it only does so when the thermostat tells it to. Let’s say you set your thermostat to 68 degrees, if that temperature is reached, the furnace takes a break until the temperature drops below 68 degrees.
- If your fan is set to “on”: it will always blow the air even when the furnace is in the down cycle. So, during this period, cold air will blow out of the vents, which could make the rooms feel miserably cold.
2) Is Someone Adjusting Your Thermostat?
It is always a good idea to double-check the temperature setting on the thermostat even when you are sure you set it right. Other folks that live with you could have inadvertently adjusted your thermostat.
Temperature comfort conditions vary from person to person and other people may have adjusted the thermostat to their comfort and at other times, they may have done it to save money.
- Low battery: Do you have a thermostat that is powered by batteries? Low batteries could be the reason why the thermostat is not working correctly. While batteries in a thermostat last long, they don’t have to be dead to start causing problems. Dying batteries affect the way a thermostat works.
So, before calling a professional to come and have a look at your furnace, make sure that you have batteries that are in good working condition.
3) Thermostat Not Compatible With Your Furnace.
With technology advancing, programmable thermostats are trending, with homeowners rushing to get one for their homes. But sometimes, the new thermostats are not compatible with older HVAC systems. In this case, to know what needs to be done, it is to call a professional to come and take a look. They will most likely get everything sorted out.
4) Dirty Furnace Air Filters
Air filters work all the time to catch dust, debris, and pollen. They can quickly become dirty and clogged. When air filters are overly clogged, they will restrict airflow into your HVAC system.
Because of that, there won’t be enough air for your furnace to distribute into your home, and the burner will quickly overheat and shut off. This could be why your furnace is not blowing hot air.
Fortunately, swapping air filters is something that you can easily do yourself. But make sure that you turn off the furnace before changing the air filters. If the color of your air filter is that of mud, then it’s a clear sign that they need to be replaced. It is always smart to replace air filters often because they can prevent other components of your furnace, such as the heat exchanger, from getting damaged, which could attract more costly repairs.
5) Condensate Line Issues
Furnaces have condensate lines that drain away water from the furnace. The condensate is among the components of a furnace that require regular maintenance. The condensing unit continuously drips water into a drip pan, eventually dripping outside your home.
If you forget to do maintenance on them, dirt will build up, and they can quickly get clogged. If that happens, the float switch will trip and, in turn, will shut off the system.
6) Leaking Air Ducts
Holes on the air duct have more of an effect than you would think. Leaks and disconnections can be due to old aging ducts but sometimes can result from rodents biting them and spoiling them.
Hot air escapes through the leaks and disconnections on the ductwork before it can reach the air vents. In turn, no hot air will blow out of the vents. This could be why your furnace is on but not blowing hot air.
Depending the on the damage, you can quickly seal the ducts with tape or new pieces. But if you are unsure if you can do it it’s best to call an HVAC technician to come and do an assessment.
7) Flame Sensor Issues
Aging and dirty flame sensors may cause your furnace not to blow hot air. Dirty sensors will cause the burner to shut off, but the fan will continue blowing. As a result, no hot air will come out of the vents. It’s all going back to regular maintenance of your heating system.
8) Clogged Burner
The burner is another component of your HVAC system that should not be forgotten when it comes to maintenance. Although they can stay much longer without any issues, sometimes they might become dirty and clogged. This will prevent fuel from coming in. The fan however will still be blowing but with no hot air.
You can solve this problem by cleaning it. But as we have always said, if you are unsure about what you are doing, it’s always smart to call a professional to come and do the job for you.
Read also: House heater blowing cold air
Final Thought on No Hot Air Coming from Furnace
There are several reasons you have no hot air from the furnace when it is turned on. Other issues are easy to sort out, and you can easily fix them yourself, while others need professional help to be sorted out. If you notice that your heating system has started giving you problems more often than usual, you may want to consider getting a new HVAC system. Frequent HVAC repairs can be more costly than a system replacement.
HVAC tech with over 30 years of experience. Retired and doing repair work on the side around Madison County, AL.