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Why Is My Furnace Not Blowing Hot Air?

As the temperature outside starts to drop, you turn to your heating system for warmth and comfort. Imagine powering on your furnace only to discover cold air is coming from your vents. What causes this issue, and how can you fix it?
This guide reveals the top causes of a furnace not blowing hot air, solutions to the problem, and how a professional HVAC contractor can help. Keep reading to discover everything you need to know about this issue and how to fix it.

Reasons Why Your Furnace Isn’t Blowing Hot Air

If you notice your furnace blowing cold air instead of hot air, you can usually narrow it down to one underlying cause. Below are some of the most common reasons why your furnace isn’t distributing warm air.

1. Your Thermostat Settings Are Wrong

If no warm air is coming through your vents, it doesn’t necessarily mean you need furnace repairs. Check your thermostat settings first to confirm it’s set to heat at your desired temperature. Glitches with your thermostat can alter the settings and cause the furnace to produce heat at a much lower temperature than you prefer.

2. The Filter Is Dirty

Heat can only circulate throughout your home when the furnace’s air filter is clean. A clogged filter restricts airflow, which can leave your home feeling cold even when the furnace is turned on. Change your filter to promote airflow, and heat should come from your vents on demand.
Replace your filter before it gets clogged with dirt and debris. Experts suggest changing the filter every one to three months, though you may need to replace yours more frequently if you have pets or multiple people in the household.

3. Electronic Ignitor Malfunction

Most modern furnaces rely on an electronic ignitor to initiate the heating process. If your furnace is failing to produce warm air, it could be due to an issue with the electronic ignitor. Various factors, such as dirt and grime build-up, routine maintenance or emergency service from the gas company, exposure to a strong burst of air, or an aging furnace, may contribute to the malfunction of the electronic ignitor. If you’re experiencing heating issues, it’s essential to address potential problems with the electronic ignitor for optimal furnace performance.

4. Issues with the High-Limit Switch

Is your furnace not blowing hot air as soon as you turn it on? The problem could lie with the high-limit switch. This piece essentially serves as a temperature control for your furnace and activates to prevent the furnace from overheating.
The high-limit switch is a furnace safety feature that can prevent your unit from experiencing major malfunctions or sparking an electrical fire. However, a faulty switch can register the furnace as falsely overheating and automatically lower the temperature. This could explain why the furnace is blowing cold air despite the thermostat settings being correct.

5. Your Furnace Has Overheated

It’s possible that your furnace overheated. If this happens, your high-limit switch kicks into gear to cool off the furnace, which is why it no longer blows hot air. What causes a furnace to overheat?
Clogged air filters tend to contribute to the problem, though there could be a mechanical failure elsewhere in the system. Overheating can also occur if you fail to perform annual maintenance or if your system is approaching the end of its lifespan.

How Do I Fix My Furnace?

Is your furnace not blowing hot air and you need a quick solution? You can troubleshoot this issue in a few different ways, depending on the cause of the problem.

Replace the Filter

A key part of furnace maintenance is regularly replacing the filter. Clogged filters can lead to furnace cycling and even cause a system breakdown. Changing your filter can reduce the chance of mechanical problems, such as the furnace blowing cold air due to overheating.

Check the Thermostat

Make sure your thermostat is working properly by checking the batteries and replacing them if necessary. You should turn the fan setting to “auto” rather than “on” so cold air stops blowing when the house reaches the desired temperature. Confirm that the thermostat isn’t set to “cool” and is at a temperature you’re comfortable with.

Clear Blocked Ducts

Much like a clogged filter, your home’s air ducts can fill with dust and debris that restricts airflow. Removing any build-up from the ducts can restore the furnace’s function and deliver heat throughout your home. You can either do this on your own or contact a technician to check for leaky ducts.

Call an HVAC Professional

If your attempts at fixing the furnace don’t help, it’s time to reach out to an expert. Licensed technicians can make sure the heating system is working properly and perform reliable furnace repairs if it isn’t. Common repairs include replacing the thermocouple to keep the pilot light lit and replacing the high-limit switch.
Other common issues that can affect your furnace’s operation include problems with the electric ignition or heat exchanger. A professional will inspect all components to evaluate the condition of your heating system and determine the best course of action.

No matter what issue impacts your furnace, Gervais Mechanical Services is here to help. We can pinpoint the reason for the furnace not blowing hot air and provide a lasting solution. Contact us today via our online form or by calling (888) 557-6616 to schedule a heating service.

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