How Do You Fix A Furnace That Blows Cold Air? Quick Tips

Don’t worry, the chill of a broken furnace doesn’t have to last.

There may be several reasons for it, like thermostat settings, gas supply, ignition, or even a dirty air filter. Try resetting the toggle button and relighting the pilot light. Check the filter too, if it’s dirty, clean or replace it.

However, if it’s something more complex, don’t take any risks, call an expert. Our HVAC experts can provide commitment estimates and quality products to improve energy efficiency, keeping your furnace running smoothly all year round.

Contact them today and get back to comfortable living.

How Do You Fix A Furnace That Blows Cold Air

Image of a air filter of a furnace

Common causes of furnaces blowing cold air

If your heating system is blowing cold air instead of warm air, it could be due to several common issues. One possible cause is a dirty air filter that restricts airflow and reduces heating efficiency. 

Another possible cause is a malfunctioning thermostat that misreads the temperature or sets the fan setting to “On” instead of “Auto”. Additionally, a problem with the gas supply, pilot light, ignition, gas valve, burners, or circuit control board can impact the heating process and result in cold air. A clogged filter, duct, drain line, or condensate line can also affect the furnace’s performance and safety features. To diagnose and fix these issues, try troubleshooting steps or contact an HVAC professional.

To prevent these issues, it’s recommended to schedule regular maintenance and cleaning for your furnace, including the air filter, ductwork, and drain lines. Also, check and adjust the thermostat settings based on your preferences and the weather conditions. Keep the areas around the furnace, vents, and heat exchanger clean and clear of debris, grime, or partials. Use high-quality filters and replace them as often as recommended by the manufacturer or HVAC experts. Furthermore, consider upgrading your HVAC system to a more energy-efficient and reliable product, such as gas furnaces or heat pumps, to improve your comfort and reduce your utility bills.

A homeowner shared a story about their furnace’s cold air issue, which turned out to be caused by a faulty flame sensor that needed to be cleaned and reset. After troubleshooting with the help of some HVAC experts, the furnace started to blow warm air again, and the homeowner felt relieved and happy. However, the incident reminded them of the importance of regular maintenance and safety checks to avoid potential damage and risk in the future.

Remember, a dirty air filter can cause cold air and high utility bills, so make sure to keep up with regular maintenance and cleaning to avoid issues with your HVAC system.

Dirty Air Filters

Filters over time, can gather dust, debris and other particles that obstruct air flow. This can lead to a build-up of ice on the evaporator coil, hindering heat transfer. In addition, a clogged filter can make the furnace overwork, resulting in increased energy consumption and higher utility bills.

Therefore, it is essential to clean or replace filters regularly as recommended by manufacturers or professionals. Dirty filters may also cause premature wear and tear of furnace parts like fans and motors. So, it is important to keep the whole heating system clean, not just the filters.

I once had a client with a furnace blowing cold air, even though it had been good before. On inspection, we realized that the filter was extremely dirty and had not been changed. After cleaning the filter, the furnace worked as new again. This experience has taught me that ignoring basic tasks like changing filters can cause severe issues with your HVAC system.

If your furnace were able to talk, it might question why you keep cranking the thermostat to freezing temperatures and expecting a hot summer.

Thermostat settings

Is your furnace blowing cold air? It could be a problem with your thermostat settings. Check if it’s set to the right temperature and heating mode. Maybe change the batteries or reset the thermostat. Your thermostat may be malfunctioning, causing the furnace to blow cold air even if it’s set correctly.

Consider getting a newer thermostat model or get help from a professional. Remember to regularly check and maintain thermostat settings. This can save you money and prevent future furnace issues. Plus, if your pilot light goes out often, check your gas supply.

Pilot Light and Gas Supply Issues

Furnace frustrations? Cold air blasting out of vents? It’s likely caused by pilot light and gas supply issues. The pilot light may have gone out, or there could be a problem with the gas supply. It may be a faulty thermocouple or dirty burner components that are to blame. Or perhaps there are obstructions in the gas line or pressure issues.

No DIY repairs! Safety first when dealing with furnace issues. Get an HVAC specialist to take a look. And don’t forget to install carbon monoxide detection as it’s better to be safe than sorry. Also, don’t forget to keep an eye on condensate and drain lines as you don’t want a cold-hearted, drained-out furnace.

Condensate lines and Drain Lines

Maintain your condensate & drain lines with a 5-step guide.

  1. Locate the line near the bottom of the furnace.
  2. Turn off all power sources.
  3. Remove dirt, dust and debris with a wet-dry vac or compressed air.
  4. Closely inspect for any leaks.
  5. Flush the line with hot water.

Remember to check & maintain regularly. Add a few drops of bleach every 3 months to prevent mold growth.

Take care of these details today, it’ll save you money & potential repairs later on.

Oh, and if your furnace’s flame sensor is acting up, it’s probably trying to audition for a horror movie.

Flame Sensor and Ignition Issues

Furnaces blowing cold air can be caused by many things. One of them is a dirty or malfunctioning flame sensor. It detects the heat from the burner flame, but if it fails, it shuts off the gas valve, giving off cold air.

Faulty ignition systems can also be the cause. The furnace might not spark at all, or it could sporadically light up, also giving out cold air.

Age and debris build-up can lead to problems with both flame sensors and ignition systems. That’s why regular maintenance checks are so important.

Don’t let your furnace become a rebellious teen. Get it checked before it leaves you in the cold during extreme weather.

Control Board Problems

If you’re feeling a chill coming from your furnace, it may be due to Control Board Problems. The Control Board commands the various operations of the furnace. A power surge or outage can damage the circuit board and cause problems. Faulty relays, which open and close circuits, can also be an issue. An old or damaged thermostat can also mess with the Control Board.

The best way to get to the bottom of this is to get a professional HVAC technician. To avoid Control Board Problems, make sure to get regular maintenance for your furnace. Don’t let the high limit switch leave you in the cold, call a repairman soon.

High Limit Switch and Fan Limit Switch

High limit and fan limit switches are important parts of furnaces. They regulate heat and ensure efficient heating. 

Let’s have a look at their functions and what can cause furnaces to blow cold air.

Switch TypeFunctionality
High Limit SwitchChecks the temperature in the furnace. Shuts off if it goes too high.
Fan Limit SwitchGets the fan going when the furnace reaches a certain temp. Faulty switches might stop the fan too soon, so cold air is blown out.

Also, clogged air ducts due to dirty filters can make your furnace blow cold air. So, it is important to clean and maintain your furnace regularly.

Change filters every 3 months. Don’t tamper with these delicate components as it can damage your furnace. For repairs, call an expert. Now, let’s get started on troubleshooting furnaces.

Furnace Troubleshooting Steps

It is essential to identify the potential concerns and troubleshoot when a furnace is blowing cold air. 

Here’s how you can fix it:

  1. Check the thermostat settings: Start by checking if the thermostat is set correctly and that the temperature is set to your preferences. Sometimes, people accidentally switch the thermostat to ‘cool’ instead of ‘heat’ mode.
  2. Check the air filter: The air filter should be clean, and any grime or dirt must be removed. Clogged filters can result in insufficient heating and airflow, causing the furnace to blow cold air.
  3. Check the pilot light or ignition: If you have a gas furnace, check the pilot light or ignition. If it’s not functioning correctly, it can result in cold air blowing out of vents.

If these steps do not solve the issue, it’s recommended to contact an HVAC professional.

A couple of unique details to keep in mind during the furnace troubleshooting process include checking the ducts and vents for partials and dirt, and resetting the toggle switch for safety mode.

I remember a customer who was experiencing the same problem with their furnace blowing cold air. Upon inspection, we found that the furnace blower motor was malfunctioning. After replacing it, the furnace was back to its warm air cycle, and the customer was satisfied.

Check the Thermostat Settings

The thermostat is integral for controlling the temperature in your home. Check your furnace thermostat when having problems. First, make sure it’s in “heat” mode, not “cool.” Then, see if the set temperature is higher than the room’s current temp. If it still won’t work, replace the battery or the entire thermostat.

Where you place the thermostat is important. Sunlight, drafts and heat sources can affect readings. So pay attention when troubleshooting. Bad thermostats don’t communicate well with furnaces, leading to inaccurate readings and unnecessary heating or cooling, and higher energy bills.

My friend had furnace issues and thought it was broken. A repairman told them their thermostat had been exchanged, but not installed correctly during their move. This caused false communication with the furnace, interrupting the heating cycle. The repairman replaced it, fixed installation mistakes, stabilized power supply and re-programmed it. Finally, peak performance was achieved.

Finally, it’s time to replace your air filter. It’s seen things which you couldn’t even imagine, but it’s time to switch it out for the sake of your furnace’s health.

Check the Air Filter

When troubleshooting furnace problems, start with checking the air filter. Ignoring it could lead to bigger issues and expensive repairs. 

Follow these steps to ensure your furnace’s longevity:

  1. Turn off the furnace.
  2. Find the air filter compartment.
  3. Gently take the filter from its slot.
  4. Check for damage or dirt build-up.
  5. Replace with one of the correct size and rating if needed.
  6. Put the air filter back in and turn on the furnace.

Remember to check and change your air filter every 3 months. This may be more often if you have pets, smoke indoors or live in a dusty area.

Stock up on filters, no late night or weekend store runs. And before you check the pilot light, make sure the gas supply isn’t empty.

Inspect the Pilot Light and Gas Supply

Inspecting your furnace is essential. Here’s a step-by-step guide:

  1. Turn off the power supply.
  2. Find the pilot light, it should be blue.
  3. Check for debris or dust.
  4. Look at the gas valve and filter, make sure they’re open and clear.
  5. Evaluate the thermocouple sensor and check for dirt or cracks.

Be careful when working with fuel-burning appliances. Don’t let minor issues become major problems. Stay on top of maintenance and inspections to keep yourself safe.

Remember that it’s all about the flame. Keep the sensor and ignition system in check.

Check the Flame Sensor and Ignition System

Having furnace troubles? Flame sensors and ignition systems might be the issue. 

Here’s a guide on how to fix it:

  1. Turn off power.
  2. Locate the sensor and clean it with steel wool or sandpaper.
  3. Use a multimeter to test the sensor’s continuity.
  4. Check wiring connections between the ignition control module and ignition sensor.
  5. Ensure proper burner operation, no delay or burning poorly.
  6. Contact an HVAC pro if all else fails.

It’s smart to regularly maintain furnace components. It can save you costly repairs.

Inspect the Control Board

To troubleshoot your furnace, inspect the control board. 

Here’s a guide:

  1. Turn off power for safety.
  2. Open up the furnace and locate the board.
  3. Look for physical damage or burn marks.
  4. Check for loose connections, corrosion, or other damage.
  5. Use a multimeter to test each component and verify if they work.

Be careful when handling the board. Don’t tamper with it unless you know what you’re doing. If in doubt, get an expert.

Unfixed problems with the board can cause serious issues with your furnace. Take action if you suspect any damages or malfunctions.

These simple steps can help you quickly identify problems and get your furnace running again. Also, check the high limit switch and fan limit switch.

Check the High Limit Switch and Fan Limit Switch

Finding a furnace that’s not functioning correctly? Inspect the high and fan limit switches. They play a big role in regulating temperature and avoiding overheating. 

Here’s the steps:

  1. Step 1: Find the High Limit Switch, usually near the heat chamber, mounted on the furnace’s plenum.
  2. Step 2: Check if it’s tripped. Press a button, or pull a knob, if it is.
  3. Step 3: Inspect and Test Fan Limit Switch, near the heating system’s blower assembly, in the warm-air supply duct. Use a voltmeter to check if it works.
  4. Step 4: Test Additional Switches. Depending on your furnace type (Gas/Electric), there could be more.

Check wiring connections too as loose wiring can indicate something’s wrong. Ensure proper insulation alsoas it keeps the switches from overheating and malfunctioning.

In the past, older furnaces lacked these essential safety devices, leading to devastating outcomes like house fires. But checking these switches regularly can keep your home safe and warm through winter.

Inspect the Heat Exchanger

The heat exchanger is an essential part of your furnace. It transfers heat to the air around your home. But, it can be easily damaged. 

This can cause problems with the furnace’s efficiency or bring health hazards. Here’s what to do:

  1. Look for cracks: Use a flashlight and feel the surface of the exchanger for any cracking or corrosion.
  2. Search for Gas Leaks: If there are signs of gas leaks, stop using the furnace right away and call a professional.
  3. Check exhaust gases: Drafts on their own show that all is working well. But, carbon dioxide, nitrogen, and water vapor should never be present.

It’s important to get an annual inspection from HVAC pros. That way, potential risks can be caught and fixed quickly.

Kevin learnt a lesson last winter when their furnace started making odd sounds. After researching, they found out cracks in the heat exchanger were causing dangerous fumes. So, keep an eye out for strange noises in your furnace.

Check the Blower Motor and Fan Setting

Checking the blower motor and fan setting of a furnace is very important in the cold months. 

Here’s a guide for doing it:

  1. Switch off the power before inspecting.
  2. Open the access panel to access the blower motor.
  3. Press the center of the belt to check the belt tension. It should have 1 inch of slack.
  4. Clean the fan blades and the housing with a brush or rag.
  5. Tighten any loose bolts on the motor and fan blades.
  6. Set an appropriate speed for the fan according to temperature and humidity.

It is better to ask a professional HVAC technician for help if unsure. Additionally, regular maintenance can help, and a clean filter is also necessary. Finally, investing in a more efficient system can lower energy costs. Don’t forget to check air ducts and vents too.

Inspect the Air Ducts and Vents

Be sure to inspect your air ducts and vents regularly. Otherwise, clogging, leakage, or obstructions could affect your furnace’s performance. 

Here’s a 3-step guide:

  1. Turn off the furnace.
  2. Look for dust or debris buildup that might block airflow.
  3. Check each vent for dirt and dust.

It’s wise to clean air ducts once a year. This keeps living conditions optimal and avoids hassles caused by blocked ducts. Plus, removing blockages in filters ensures proper airflow, thus reducing energy consumption and saving you money.

Weirdly enough, an HVAC tech in eastern Utah once found dead rodents blocking a family’s ventilation system. This caused their furnace to overheat, so it’s clear that checking your ducts is highly important. Before worry strikes, make sure nothing else is amiss, like a family of rodents living in your furnace.

Check for any Other Issues

When troubleshooting your furnace, it’s critical to check for any other issues. Skipping this step could lead to misdiagnosis and more problems. 

Follow these 6 steps:

  1. Confirm the thermostat is working and set correctly.
  2. Check air filter and clean or replace if needed.
  3. Ensure all registers and vents are open and unblocked.
  4. Inspect ductwork for any leaks or damage.
  5. Check gas supply valve is open and supplying gas.
  6. Look for signs of electrical or mechanical damage.

Don’t neglect these steps. It can save time and money. Before calling a pro, make sure you check all potential culprits. Having a properly functioning furnace guarantees comfort during cold seasons, safety, and peace of mind. So, don’t forget regular maintenance checks for optimal performance. Take care of your furnace now. Avoid DYI furnace repairs, it could turn your home into a hot mess.

Professional Furnace Repair and Maintenance

Furnace repair and maintenance are important aspects of ensuring a functional HVAC system. Regular furnace maintenance ensures optimal performance by identifying and fixing any issues before they damage the system. Repairing furnaces promptly minimizes the risk of breakdown and ensures safety for the homeowner. A professional HVAC technician provides expertise in inspecting, cleaning, and repairing the furnace.

To ensure a properly functioning furnace, it is essential to maintain it and replace air filters regularly. Dirty air filters limit airflow and reduce heating efficiency, leading to higher utility bills. 

Additionally, clogged filters can damage the limit switch, causing the system to cycle on and off frequently. Furnace repair and maintenance involve checking for clogs, debris, or grime in the ducts, air filters, and other areas.

It’s crucial to replace filters regularly and check for signs of wear or damage to the furnace system. A professional HVAC technician can inspect heat exchangers, burners, and pilot lights to ensure safe and efficient function. Other areas of inspection include the fan limit switch, flame sensor, ignition, gas valve, and blower motor.

Furnace repair and maintenance require expertise, commitment, and precision. A reputable HVAC professional identifies and solves issues promptly, saving time, money, and energy. Contact a trusted local carrier dealer or HVAC expert to schedule a maintenance or repair service call.

Fact: According to the US Department of Energy, replacing a clogged filter with a clean one can reduce energy consumption by 5-15%.
If you’re smelling gas or your furnace is acting like a rebellious teenager, it’s time to leave it to the experts.

When to Call a Professional HVAC Technician

To keep your furnace functioning well, you should fix any issues that arise. Sometimes you can sort them out yourself, but sometimes it’s best to call a professional HVAC technician

Here are a few signs that tell you when you should ask for their help:

  1. If your furnace is making weird noises or smells strange, it’s time to call in the experts. This could mean there are leaks or blockages, which could be dangerous.
  2. If your furnace isn’t heating up properly or has stopped working, it’s best to leave it to the pros. They can diagnose and fix the problem safely.

On top of that, regular maintenance checks by professionals can help your furnace perform better and keep utility bills low. Make sure to schedule annual maintenance services to spot any potential issues before they cost you a lot.

Pro Tip: Don’t forget to clean and maintain your HVAC systems. This will improve air quality and the performance of your appliances.

HVAC Professional Installation Process

When installing HVAC, hire professionals. The process changes for each system, but generally expect this:

  1. Consultation: A technician will assess your home’s heating/cooling needs and recommend a system.
  2. Installation: Technicians prepare ductwork and electrical components.
  3. Testing: Check airflow and there functionality.
  4. Configuration: Change settings for optimum performance.
  5. Maintenance: Schedule regular filter changes and inspections.

Before hiring, check for licensing and nsurance. Improper installations can cost 15% energy efficiency, as per National Renewable Energy Laboratory. Don’t risk more money and time on remedying mistakes, only hire licensed profrssionals that follow industry standards. Clean HVAC system means clean conscience and lower energy bill.

HVAC Maintenance and Cleaning

As homeowners, it’s crucial to keep your furnace working correctly and toasty warm during winter. To do this, maintenance and cleaning of your HVAC system are essential. 

Here’s a 6-step guide:

  1. Check Air Filters – Replace them regularly, dirty filters block airflow.
  2. Clean the Coils – Dirty condenser coils reduce efficiency, clean them with a fin comb.
  3. Clean the Blower Assembly – Remove debris to boost airflow and efficiency.
  4. Lubricate Moving Parts – Reduce friction and wear with lubrication.
  5. Inspect Electrical Connections – Check for frayed wires or broken connections which can cause an electrical fire.
  6. Test System Controls – Make sure they operate accurately, efficiently, and safely.

Schedule Furnace Repair yearly with certified technicians for best performance. This way, licensed professionals like NATE members can detect small issues before they become huge problems. It keeps operations running smoothly throughout winter.

A few years ago, homeowners knew nothing about HVAC maintenance. So, they often forgot to service their units until something went wrong. That’s why it’s smart to learn more about furnace repair and maintenance for cozy winters. Do regular maintenance on your furnace, or it won’t heat your home when you need it most.

Regular Furnace Maintenance Tips

When it comes to your furnace, upkeep’s essential. It’ll not only last longer but also prevent pricey repairs. Here are three tips to keep it in good shape:

  • Change or clean filter every 1-3 months.
  • Clear vents and registers from dust and debris.
  • Check the furnace belt for wear and tear, replace if necessary.

Plus, proper airflow’s key to make sure your furnace’s at its best. Schedule a pro inspection annually. They’ll examine electrical connections, gas pressure, and combustion efficiency.

A Pro Tip for maintaining your furnace such as don’t DIY complex fixes. Call a pro for repairs or replacements, to avoid damage to the system.

Your furnace may break down, but don’t let your humor. Keep it repaired and maintained just like your HVAC system.


If your furnace is blowing cold air, there could be several reasons. From simple, like a clogged filter, to complex, like a malfunctioning system. Check the thermostat settings, reset the switch, and look at the pilot light. If these don’t work, contact an HVAC expert. They’ll diagnose and repair the problem, for safe and efficient furnace use. To keep it working properly, remember to perform regular maintenance. Change the filter often, clean ducts and lines, and get yearly inspections. This extends the furnace life and efficiency, and keeps you and your family safe. For extra efficiency, seal air ducts/vents, get a programmable thermostat, adjust fan settings, and invest in energy-saving products. Familiarize yourself with furnace basics to resolve small issues and save money. But when dealing with gas, take extra caution. Gas valves and burners can be dangerous. Always rely on professionals for those tasks.