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Is Your Heater Blowing Cold Air? Here’s Why.
11 Dec, 2019

Is Your Heater Blowing Cold Air? Here’s Why.

Are you turning on your heater before bed and waking up in the middle of the night to ice cold air coming through the vents? You may think that a heater blowing cold air is uncommon but you’re not alone. Many residents along the California Coast are calling into smart72 daily, stating that their home is ice cold while their heater is blasting during winter. This “Ice Cold Heater” dilemma is sweeping the California coast and is spreading across San Luis Obispo County, Santa Barbara County, Monterey County, Santa Cruz County, Santa Clara County, San Benito County, and more. The weather inside should not be frightful, only outside, during this wonderful holiday season.

This article will address some of the most common causes of gas and electric heaters blowing cold air instead of heating properly. We will work our way from the most likely causes to the least probable.

First Thing’s First

With a heater blowing cold air, the first question to address is whether the cold air is blowing from the furnace right after the heater is turned on. Neither your air conditioning nor your heater will be cold or hot right after you turn them on. Just like the hot water doesn’t run in your faucet immediately after you turn it on, it takes time for the recently heated air to travel through your ducts to your registers and into your house. An electric heater and a gas furnace blowing cold air will be exactly the same, so give it a few minutes after you turn it on. It will also depend on how much insulation you have around your ducts and how old your furnace is. Like they say, patience is a virtue.

Thermostat Installation San Luis Obispo, CA 93401

The Most Common Culprit Is The Thermostat

Setting The Thermostat Properly: Ensure that your thermostat is set higher than the temperature in your home. Otherwise, your electric heater or gas furnace will not turn on.

Make Sure You’re Turning On The Right System: Additionally, you will want to make sure that you turn on the right piece of equipment. Your furnace and your air conditioner are designed to do the complete opposite things. You would be surprised at the number of calls we get where customers are manually turning on their Air Conditioner to heat their home and Furnace to cool their home, by accident. You never want to turn the Air Conditioner on and set the temperature to 76 degrees in an attempt to heat your home.

Battery Maintenance: Another possible culprit for your heater blowing cold air is the batteries in your thermostat. Some thermostats are connected to central power and some have central power with a battery backup, but what some people don’t realize is that there are some thermostats that work on batteries only, so check your thermostat and replace your batteries regularly.  It is also important to know that the batteries don’t have to be completely dead for your thermostat to act up.  This can cause your heater to blow cold air due to improper temperature inputs from the thermostat.

Check Your Ductwork

Have you ever climbed up in your attic or gone down into your basement to check out your ductwork? No? Thought so. Most homeowners have never even seen the ductwork in their home. We like to think of the ductwork as being the veins of the home, while the furnace and air conditioner are the vital organs. Just like going to the doctor’s, it is important to get regular check-ups on your HVAC system ensure the health of your home’s heating and cooling system.

If you do decide to take a peek up in your attic at your ductwork, be careful! You don’t want to go through the ceiling. Make sure that you only walk on the joists, the wooden planks running across your attic (usually 2X4’s).

Leaks and Tear in Ducting: A heater blowing cold air could be a result of a leak or tear in your ducting.  Over time, the changing temperatures wear on all sorts of things and your ductwork is no exception.  Your ducts are usually in the attic and outside of your insulation, exposing them to the freezing cold. Ensure the that you check these before proceeding to the next step because these can be an easy fix but a serious problem.  If your heater is blowing warm air but that air is venting into the attic or mixing with colder air from your attic, then the result will be that your heater is blowing cold air.

Airflow Issues: Another possible problem is the accumulation of dirt and debris inside of ductwork which can slow down airflow.  This problem is rarely (very rarely) severe enough to fully block airflow, but it is worth looking into.  If airflow is blocked too much, it can cause your heater to overheat which can cause it to kick off as a safety precaution.  This would not result in a heater blowing cold air, however, and would be an entirely different problem.  If you think this is the issue, please call 888-757-0997 for immediate assistance.

For more information on reasons to get your ductwork cleaned, click on the link below:

Should You Have the Air Ducts in Your Home Cleaned?

Check Your Pilot Light

However, if cold air continues to blow through your heating unit then it is more likely to be a serious issue. Electric heaters would not need to worry about this portion.

Check Your Pilot Light: The next step is to check your pilot light.  A pilot light is a small flame that is burning constantly to ensure that your heater can ignite easily (rather than relying on an ignitor that can fail).  These can be blown out sometimes though, usually as a result of the gas company shutting down lines for maintenance or emergencies.  For information on how to check your pilot light, try the following video:

If you are unable to determine if your gas furnace is receiving the proper gas supply, then try another gas appliance in your house.  Often times if you have a gas furnace then you will also have a gas stove and oven, so start there.

Check the Filter

Furnace filters ensure that contaminants don’t get into the heating system which ensures that everything is running smoothly.  These become clogged sometimes, so you need to ensure that you are changing them regularly. Fortunately, they are pretty inexpensive and easy to change.  A furnace blowing cold air is not going to happen for no reason, so keep working your way up from most obvious to least obvious. If you have a furnace blowing cold air then try this quick video on how to change your filter:

If your Furnace is Still Blowing Cold Air, Check Your Flame Sensor.

If your heater starts circulating warm air out of your registers at first but then turns blowing cold air, then you may need your flame sensor to be cleaned. If your flame sensor is encrusted with residue and carbon, then it will initially turn on but will quickly lower the temperature due to inaccurate readings. Start by taking a look at it to ensure that it is in good shape, then clean it by using the following method:

How to Clean a Furnace Flame Sensor

If You Still Have a Heater Blowing Cold Air, Now You Call in the Pro’s.

At some point, no matter how much you know, it is just simpler and cheaper to call in the pros. A licensed HVAC contractor will have a far better idea of how to fix a heater that is blowing cold air than your average Joe. You’d change the oil in your car, but would you attempt to replace the transmission? Probably not, and in the end, you’d end up paying far more than you would have if you had gone to a heating professional in the first place.
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Heating and Cooling San Luis Obispo, CA 93401