Furnace Blows Cold Air Sometimes?


Have you ever experienced the frustration of your furnace blowing cold air sometimes? We understand how inconvenient and uncomfortable it can be.

In this article, we will explore common reasons behind this issue and provide solutions to help you resolve it. From thermostat issues to clogged air filters, malfunctioning pilot lights or ignition systems, lack of maintenance, and ductwork problems – we’ve got you covered.

Let’s get your furnace working efficiently again!

Thermostat Issues

Sometimes the thermostat doesn’t accurately control the furnace temperature. It’s frustrating when you set the thermostat to a certain temperature, but instead of warm air, you get cold air blowing out of the vents. We’ve experienced this issue before and it can be quite uncomfortable, especially during colder months.

When the thermostat malfunctions, it can lead to inconsistent heating in your home. One possible cause could be a faulty temperature sensor within the thermostat itself. This sensor is responsible for detecting the current temperature and relaying that information to the furnace. If it becomes inaccurate or damaged, it will send incorrect signals to the furnace, causing it to blow cold air when you expect warmth.

Another potential culprit could be an issue with the wiring between the thermostat and the furnace. Over time, wires can become loose or damaged, resulting in poor communication between these two components. As a result, commands from the thermostat may not reach the furnace correctly, leading to erratic heating patterns.

To fix these issues with your thermostat, it’s best to consult a professional HVAC technician like ALP Heating who can diagnose and repair any underlying problems. They have experience working with thermostats and furnaces and will be able to determine whether replacement parts are necessary or if recalibration is sufficient.

Clogged Air Filters

A common cause of a furnace blowing cold air is clogged air filters. When our air filters get clogged, they restrict the flow of warm air through the system, causing it to blow cold air instead.

Here are five things to consider when dealing with clogged air filters:

  • Regular maintenance: It’s important to regularly check and clean or replace our air filters to ensure proper airflow.
  • Efficiency: Clogged air filters can decrease the efficiency of our furnace, leading to higher energy bills.
  • Indoor Air Quality: Dirty filters can also lead to poor indoor air quality as they fail to properly filter out dust, pollen, and other allergens.
  • System lifespan: Neglecting filter maintenance can put extra strain on our furnace, potentially shortening its lifespan.
  • Heating performance: A clean filter allows for better airflow and heat distribution throughout our home.

By addressing these factors and ensuring regular filter maintenance, we can help prevent the problem of a furnace blowing cold air due to clogged air filters.

Malfunctioning Pilot Light or Ignition System

When the pilot light or ignition system malfunctions, it can cause the furnace to blow cold air. This is something that we have experienced firsthand in our home. It can be quite frustrating to wake up on a chilly morning only to find that the furnace is not working properly and blowing out cold air instead of warm air.

One time, we woke up to find our house unusually cold. We checked the thermostat and realized that it was set to a comfortable temperature, so there must have been something wrong with the furnace itself. After some investigation, we discovered that the pilot light had gone out.

We quickly followed the manufacturer’s instructions and relit the pilot light. However, even after doing so, we noticed that the furnace was still blowing out cold air intermittently. This indicated that there might be an issue with the ignition system as well.

It is essential to address any issues with your furnace’s pilot light or ignition system promptly. Neglecting these problems can lead to further complications and discomfort in your home. Therefore, if you notice your furnace blowing out cold air when it should be warming your space, don’t hesitate to seek professional help.

Lack of Maintenance

If you neglect regular maintenance, your furnace may not function properly and could cause discomfort in your home. As homeowners ourselves, we understand the importance of keeping up with furnace maintenance to ensure our homes remain cozy and warm during the colder months.

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Essential Regular Maintenance Tasks for Optimal Furnace Performance

Regular maintenance involves simple tasks that can make a big difference in the performance of your furnace. One crucial step is regularly changing or cleaning the air filters. Clogged filters restrict airflow and force your furnace to work harder, leading to inefficient heating and potential breakdowns.

Another essential aspect is inspecting and cleaning the blower motor. Over time, dust and debris can accumulate on the blower wheel, reducing its efficiency. A quick vacuum or wipe-down can go a long way in preventing issues.

Importance of Calibrating Thermostat Settings for HVAC Efficiency

We also recommend checking the thermostat settings periodically to ensure they are correctly calibrated. Incorrect temperature readings can lead to inconsistent heating or even a complete shutdown of your furnace.

scheduling an annual professional inspection is vital for detecting any underlying problems early on. HVAC technicians have extensive knowledge and experience in identifying potential issues that may be invisible to untrained eyes.

Ductwork Problems

To ensure efficient heating in our home, we regularly inspect and clean the ductwork for any obstructions or leaks. Ductwork problems can often be the cause of a furnace blowing cold air sometimes. Over time, dust, debris, and even pests can accumulate in the ducts, blocking airflow and reducing the effectiveness of our heating system. Additionally, leaks in the ducts can allow warm air to escape before it reaches its intended destination.

To help you understand common ductwork problems and their potential solutions, we have created a table below:

ProblemPossible Solution
Accumulated debrisClean out the ducts regularly to remove any buildup
BlockagesInspect and remove any obstructions from the ductwork
LeaksSeal any gaps or holes in the ducts to prevent air loss
Inadequate insulationAdd insulation around exposed sections of the ductwork

Furnace Blows Cold Air – FAQ

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How can I troubleshoot and fix a furnace that is blowing cold air sometimes?

To troubleshoot and fix a furnace that blows cold air intermittently, we can follow these steps.

– First, check the thermostat settings to ensure they are correct.
– Next, examine the air filter and replace it if dirty or clogged.
– It’s also important to inspect the pilot light or ignition system for any issues.
– Additionally, check the ductwork for blockages or leaks.

If these steps don’t resolve the problem, it’s best to consult a professional HVAC technician for further assistance.

What are some common signs of thermostat issues that could cause a furnace to blow cold air sometimes?

Some common signs of thermostat issues that could cause a furnace to blow cold air sometimes include incorrect temperature readings, frequent on/off cycling, and unresponsive controls.

These problems can occur due to faulty wiring, sensor malfunctions, or a need for recalibration.

It is important to address these issues promptly by checking the thermostat settings, replacing batteries if needed, and contacting a professional HVAC technician for further diagnosis and repairs.

How often should I change my furnace’s air filters to prevent it from blowing cold air sometimes?

We should change our furnace’s air filters regularly to prevent it from blowing cold air sometimes. The frequency of filter changes depends on various factors such as the type of filter, the number of pets in the house, and the overall air quality.

As a general guideline, it is recommended to replace standard 1-inch filters every 1-3 months, while high-efficiency filters may need replacement every 6-12 months.

Regularly changing air filters helps maintain proper airflow and ensures consistent warm air circulation from the furnace.

Are there any specific steps I can take to troubleshoot and fix a malfunctioning pilot light or ignition system causing the furnace to blow cold air sometimes?

There are specific steps we can take to troubleshoot and fix a malfunctioning pilot light or ignition system that may cause the furnace to blow cold air sometimes.

First, check if the pilot light is lit. If not, relight it following the manufacturer’s instructions.
Next, ensure that the gas supply valve is open and there are no blockages in the gas line.

If these steps don’t solve the issue, it’s recommended to contact a professional HVAC technician for further assistance.

What are some important maintenance tasks I should regularly perform to prevent my furnace from blowing cold air?

Some important maintenance tasks we should regularly perform to prevent our furnace from blowing cold air sometimes include:

– Cleaning or replacing the air filters
– Inspecting and cleaning the blower motor
– Checking for any blockages in the vents and ducts
– Ensuring proper thermostat settings
– Scheduling regular professional inspections and tune-ups


In conclusion, it’s important to address the issue of a furnace blowing cold air sometimes. By identifying the possible causes such as thermostat issues, clogged air filters, malfunctioning pilot light or ignition system, lack of maintenance, and ductwork problems, we can take proactive steps to resolve the problem.

Regularly checking and maintaining these components is crucial for ensuring that our furnace operates efficiently and provides consistent warmth throughout our home.

Don’t ignore this issue; instead, take action to keep your furnace running smoothly and effectively.

Schedule a Furnace Inspection Today!

Reliable Furnace Cold Air Repair in Your GTA Home

ALP Heating is committed to providing the finest service possible to important areas. We are delighted to be your go-to cooling and heating business for all of your requirements. Because of our commitment to perfection.