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Why Is My Heating Unit Blowing Cold Air?

When the cold season sets in, the furnace becomes one of the most important devices in our homes. Everyone wants to check whether it’s working well to guarantee the much-needed warm indoor temperatures.

But what happens when you find out that your heating unit is blowing cold air? Going home to a cold home is never a pleasant situation. And finding the solution to that problem instantly is crucial.

Many homeowners will, at one point, face this question – why is my household heating unit blowing cold air? 

And here are the top reasons:

Heating Unit Blowing cold Air — Nine Reasons Why

  1. Wrong Thermostat Settings

If you are wondering, “why is my heating unit blowing cold air?”, the first and somewhat obvious reason your furnace may be blowing cold air is the thermostat. If it’s not set on “heat” mode, it will only circulate cold air.

This might be the simplest reason, but it’s also one that many homeowners will encounter. Therefore, before you overthink why your home is not heating up, check on that small device. Make sure the switch is turned to heat mode.

  1. Dirty Air Filter

The air filters work to clean the air getting into your house. And if these filters are too dirty or clogged, it means that the airflow in the unit is compromised.

When there’s no sufficient airflow reaching the heat exchanger, it means that the air is not heated. And only cold air gets blown into the house.

Besides the cold air, the next thing will be the overheating of the unit. And as a result, the high limit switch will trip as a safety measure. When the high limit switch trips, the furnace will shut down altogether.

The solution here is to clean or replace the air filters.

  1. Dirty Flame Sensor

This small device directs your gas furnace when to turn on and heat the air circulating through the house. If the sensor is dirty, it might not detect when the furnace or heaters should turn on. And in that case, your furnace will only blow cold air.

The solution to this problem is pretty straightforward – clean the flame sensor. But if you are not up to the task, don’t hesitate to contact a professional HVAC technician. They are well versed with the system and will also help establish if there is another underlying problem.

  1. Leaking Ductwork

This might sound improbable, but it can undoubtedly cause cold air to be blown into your house. How? You might ask.

Well, when there are leaks in the ductwork, the warm air gets released before it even reaches the vents. Also, cold air might be drawn into the ductwork through the leaks, dropping the temperatures of the circulating air.

The end result is cold air reaching your indoor space or insufficient heating. And to solve this, ensure you’ve sealed all the leaking points. An HVAC technician will be best suited to do this job.

  1. Low Refrigerant Level

This problem is only common in heat pumps and not furnaces. Usually, the refrigerant helps to absorb heat from the outdoors and then transfers it indoors. And if there’s a leak, it means that there won’t be enough heat transfer, which will eventually lead to your unit blowing cold air.

Therefore, if you are using a heat pump to warm your home, ensure that there’s enough Freon in the refrigerant line. Otherwise, you’ll continue experiencing cold air in the room, even when you direly need it warm.

However, there’s one crucial thing to note here – don’t try to refill the refrigerant yourself. The process is quite dangerous and should only be undertaken by a professional.

  1. The Furnace Hasn’t Heated Up

My heating unit is blowing cold air despite everything looking okay – what might be the issue? Someone might ask.

Sometimes, your heating unit blowing cold air isn’t really a problem. In fact, it might be just that it hasn’t warmed up.

Usually, some furnaces will take longer to heat up and warm the air blowing into your house. This is common when the heater has been dormant for a long time, especially after a hot season. 

Therefore, you might just need to give it some time to heat up.

But if the problem persists, call your HVAC technician to take a look at it. 

  1. Clogged Condensation Line

Every technology advancement has its pros and cons. For instance, the new and energy-efficient heating units have a condensate drain line. This is meant to drain the condensate generated during the heating process.

Now, when the drain line is clogged, it can’t drain the condensate. And when this condensate backs up, it hinders your furnace from heating the air.

Unclogging the drain line and finding a permanent solution for it is the ideal solution.

  1. Other Thermostat Issues

As mentioned earlier, a thermostat is quite vital as it helps to set the desired temperatures in the room. As a result, when the temperatures drop beyond that point, the heater turns on. But, if the thermostat has issues, this won’t happen.

For instance, if the thermostat batteries are dead, the thermostat can’t send the correct signal to the furnace. Consequently, your furnace might not turn on when it should.

It would help if you also kept in mind that some older model furnaces don’t work with new digital thermostats. So, ensure you’ve chosen a compatible one for your system.

  1. Pilot Light Going Off

While many newer heater models don’t have a pilot light, the older models do. And many people are still using such furnace models.

The pilot light helps to ignite the burners when the furnace is turned on. If it’s out, the burners won’t ignite, and your furnace will fail to heat the air.

Therefore, if you have an older model with pilot light and it keeps going off, ensure you’ve followed all the relighting instructions in the user manual. For example, turn off the thermostat and relight the pilot light (either manually with a lighter or via a button in modern furnaces).

If that doesn’t work, call in a professional as there might be another problem.

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