During winter, there is no time to encounter a furnace blowing cold air. It makes your San Antonio, TX, home less comfortable than it should be. Allowing the problem could result in higher energy costs and more damage to your HVAC system. Learning how to troubleshoot your furnace when it blows cold air can help you get it running again.
In this post, bluefrog Plumbing + Drain + HVAC of San Antonio walks you through some of the reasons why your furnace is blowing cold air and when to call the local AC company.
Dirty Furnace Filter
A furnace filter covered in dirt and grime will make it difficult for air to pass through and get to the heat exchanger. This means that there is insufficient air to heat and redistribute. The result is long heating cycles and your furnace blowing cold air.
The furnace filter is a critical component that affects the efficiency of your furnace. We recommend calling an AC company regularly to clean the air filter and change it every three months.
Wrong Thermostat Settings
The thermostat is one of the first places to check if your furnace is blowing cold air. It’s easy to get the thermostat settings wrong, especially as the weather changes from summer to fall, and you turn the furnace on for the first time in a year. If the furnace is blowing cold air, maybe it’s because you set it for the hot weather and never changed it when winter came around.
You want to ensure that the thermostat is set to “Auto” rather than “On.” The latter setting causes the fan to blow even when the furnace is turned off. On the other hand, the “Auto” setting triggers the furnace and fan to come on at the same time as intended.
There is also a chance that the thermostat is malfunctioning. The problem could be a variety of things – no power coming to the thermostat, dust affecting the interior mechanics, or the thermostat is at the end of its days. Whatever the case, you’ll need the expertise of an AC company to diagnose and resolve it.
Furnaces are prone to overheating, like most electric appliances. When your furnace overheats, it triggers the temperature limit switch and shuts down the heating cycles. This causes the furnace to blow cold air.
But what causes the furnace to overheat?
Restricted airflow is the most common reason for an overheating furnace. Air has to pass through the air filter before going through the heat exchanger. A clogged filter makes it difficult for air to move through the screen and get to the furnace. It causes the fan to work harder to pull air into the heat exchanger, causing your furnace to overheat.
Another cause of an overheating furnace is mechanical failure. Furnaces experience operational wear and tear over time, especially those that don’t get proper maintenance. Components wear out and lead to severe issues.
The best way to fix such issues is to call a professional to inspect and repair your furnace. However, a dose of prevention is best. Ensure you schedule regular tuneups and inspections from the local AC company. This will ensure that all components are in top shape and keep the furnace from overheating.
Damaged Pilot Light
Newer furnaces use different lighting methods. Electric furnaces don’t require a pilot light and ignite like a gas stovetop. They use an electric ignitor that creates a spark and lights up the burner, eliminating the need for a pilot light.
Older furnaces have a small flame that runs all the time, known as the pilot light. It is required to turn on the furnace burner. If the pilot light is damaged, the furnace will certainly blow cold air into your San Antonio, TX home. If relighting the pilot light doesn’t work, call the AC company to get it replaced.
Faulty Circuit Control Board
Sometimes the culprit is a faulty circuit control board. The circuit control board is the furnace’s brain and relays instructions to different components. When it receives the heating cycle command from the thermostat, it sends out signals to turn on the furnace blower and burner. However, it may fail to do that job properly if it fails.
There are many reasons why your furnace’s circuit control board may malfunction. The most common one is a lack of maintenance. A furnace leaking water can also cause permanent damage to the circuit control board. Call an AC company in San Antonio to fix any furnace problems you might have before they cause other issues like no heat.
Dirt and Grime on the Flame Detector
Some gas furnaces rely on a flame detector to ensure a successful heating cycle. If the device is covered in dirt and grime, you’ll quickly lose heat, and the furnace will begin blowing chilly air. This is an easy issue to fix, as you only need to clean the flame sensor in the furnace. Better yet, let your local AC company sanitize the flame detector and restore the furnace to full function.
Condensate Line Blockage
High-efficiency furnaces produce condensation, which exits through the condensate line. A blockage in that line causes the system’s overkill switch to turn off the unit, preventing water loss. A blocked condensate drain line may occur due to debris buildup, slime or algae growth, and restriction at the end of the line.
The best way to prevent all of the above is to conduct regular maintenance. Ensure the coils are cleaned, and the filter is changed regularly. Call an AC company to repair the issue if it’s too late and there’s standing water around the unit.
Cracked Heat Exchanger
Another possible reason for the furnace blowing cold air is a cracked heat exchanger. A cracked heat exchanger causes carbon monoxide to leak out of the furnace. This leads to carbon monoxide poisoning, which can be fatal. What’s even more frightening is that you may not know you have a cracked heat exchanger until it’s nearly fatal. Prevention is the best cure, and that means having the local AC company regularly inspect and repair your furnace.
Call a Trusted Heating and Air Conditioning Company in San Antonio
We hope you’ve gained insight into what could be causing the furnace to blow cold air, and we are happy to help. Our heating and AC experts have vast experience restoring convenience to San Antonio, TX homeowners. Call bluefrog Plumbing + Drain + HVAC of San Antonio today if you’re experiencing any problems with your HVAC system.