Why is My Furnace Blowing Cold Air? Top Troubleshooting Tips

Why is My Furnace Blowing Cold Air

Key Takeaways

  • A clogged air filter blocks out warm air, making the furnace blow cold. Change or clean filters regularly for optimum efficiency.
  • Clogged Air Filter, Pilot Light Issues, Malfunctioning Thermostat, Lack of Gas Supply, Dirty Flame Sensor, Faulty Fan Limit Switch, and Ignition Problems are some of the potential reasons that could cause your furnace to blow cold air.
  • According to Energy.gov, heat takes up 42% of household energy in the US. Maintenance and cleaning can save you 30% on energy bills and extend your furnace life. So, get pro advice and save yourself a thrill!
  • Regularly assessing and maintaining your furnace is essential. Ignoring it can lead to reduced efficiency, high energy bills, or even complete breakdowns.

Common Reasons for Furnace Blowing Cold Air

To solve the issue of your furnace blowing cold air, let me guide you through some common reasons behind this problem. Clogged Air Filter, Pilot Light Issues, Malfunctioning Thermostat, Lack of Gas Supply, Dirty Flame Sensor, Faulty Fan Limit Switch, and Ignition Problems are some of the potential reasons that could cause your furnace to blow cold air. We will discuss each of these sub-sections briefly to help you diagnose and troubleshoot the issue.

Clogged Air Filter Of Furnance

The furnace is blowing cold air? Blocked filtration could be to blame. A clogged air filter blocks out warm air, making the furnace blow cold. Change or clean filters regularly for optimum efficiency.

Inefficient airflow caused by a clogged filter? You’ll get less comfort and higher energy bills. Worse still, damage to the furnace’s heat exchanger, carbon monoxide leaks. To avoid such issues, use high quality filters with good MERV ratings. Plus, keep your furnace maintained with a professional tune-up every year.

If you have pets or live in a dusty area, check and replace your filters more often. Keep that furnace warm!

Pilot Light Issues Of Furnance

Your furnace is blowing cold air? It might be an issue with the pilot light. A thermocouple malfunction, drafts or clogs in the pilot assembly can cause it to go out.

  • Check if the pilot light is lit. 
  • Then, relight it following the manufacturer’s instructions. 
  • If it won’t stay lit, there may be debris blocking its flow or a broken thermocouple. 
  • These require an expert technician to replace them.
  • Be careful when dealing with gas flames. 

Use caution and only let someone competent handle the tools. Schedule routine maintenance at least once a year to avoid future drama.

Malfunctioning Thermostat Of System

Is your furnace blowing out cold air instead of warm? It may be due to a dysfunctional temperature control device. The thermostat is not detecting changes in the indoor temperature, and giving faulty signals to the heating system. This can lead to incorrect settings – and cold air!

  • For accuracy, the thermostat needs to be in top condition. 
  • Even minor issues can blow cold air from your furnace. 
  • Check its settings or battery if you suspect a problem. 
  • And call in a professional HVAC technician if needed.

Regular maintenance can help reduce the risk of this malfunction reoccurring. Monitor the temperature readings, and make sure your thermostat is functioning properly. Looks like your furnace needs some extra TLC – better stock up on beans and burritos for backup warmth!

Lack of Gas Supply To Furnance

The furnace may be blowing cold air due to an inadequate gas supply. Check if the gas valve is open and working correctly. Check for any blockages in the gas line or meter. If it’s a propane tank, it needs enough fuel levels.

For prevention, get regular maintenance from an HVAC technician. They’ll be able to spot potential issues before they become major ones. Having regular maintenance reduces the risk of breakdowns and service calls. Keeping the heating system in good condition means it will operate safely and efficiently all winter.

Dirty Flame Sensor Of Furnance

The flame sensor may be the cause of a furnace blowing cold air. It can get clogged with dirt and grime, so it can’t detect a flame. If this happens, the furnace can shut off or run without heat.

To clean the sensor, turn off the furnace’s power and take out the burner assembly. Then, clean it with steel wool or sandpaper. Put the assembly back in and test it.

Note that a dirty flame sensor isn’t always the problem. Other issues like faulty ignitors or gas valves might be to blame too.

Older furnaces don’t have sensors, they use a pilot light to detect a flame. But newer models use sensors for better efficiency and safety.

Faulty Fan Limit Switch Of Furnance

The fan limit switch is the culprit for a furnace blowing cold air. It helps regulate the temperature by switching on and off the blower fan. If it malfunctions, the fan may run continuously without warm air.

Moreover, the switch can stop the furnace from igniting. This usually happens when the switch gets dirty so it can’t read the temperature correctly. Then the furnace only blows cold air.

It’s essential to get the switch fixed right away, as it could damage other parts of the furnace and create safety issues. Last year, someone experienced this issue and called an HVAC technician to replace the faulty component. Thanks to their prompt action, they saved money.

Don’t let the furnace play hard to get. Fix the fan limit switch quickly.

Ignition Problems Of Furnance

Ignition is at the core of furnace functioning. Without it, your furnace won’t make heat and will only give out cold air. Malfunctions or lack of ignition can cause problems, like pilot light and igniter issues. It’s better to hire a professional to fix the issue and keep it safe and operating efficiently. Maintenance is essential for preventing this.

A dirty or malfunctioning flame sensor can cause ignition failure. This sensor checks if gas is flowing through the burners, and will shut off the gas valve if not. With time, residue on the sensor probe can make it malfunction and shut off often. Cleaning or replacing the sensor can solve this.

Another cause can be a clogged burner assembly. Debris and dirt in it can stop proper airflow and combustion, thus creating insufficient heat. Professional cleaning can help avoid this.

In fact, 75% of no-heat calls are caused by lack of maintenance, not equipment failure, according to Trane Technologies®. Regular maintenance could have prevented many heating issues over time. So don’t try to DIY your way out of a cold furnace! (Though it’s tempting.) Hire a professional!

DIY Troubleshooting Steps for Furnace Blowing Cold Air

To troubleshoot your furnace blowing cold air, you can take various steps at home without seeking professional help. In this section, you will learn about the simple DIY steps for fixing the issue. The sub-sections include checking the air filter, inspecting the pilot light, adjusting thermostat settings, checking the gas supply, cleaning the flame sensor, testing the limit switch, and ignition inspection and reset.

Check the Air Filter Of the Furnace

A homeowner discovered their furnace was blowing cool air during winter. Inspection showed a dirty filter was blocking airflow. So, they changed the air filter to a compatible model. Instantly, their home was warm again.

  • To avoid a similar issue, check the appearance of the filter. 
  • If there’s a lot of dust, dirt, or other particles, replace it. 
  • Ensure the filter is securely in place. 
  • Use the manufacturer’s instructions and replace the filter every 3 months at least. 
  • Also, clean sensors and coils on a regular basis.

Find out how to change the filter. Look at the packaging when you buy new filters or check the furnace user manual. Don’t forget to inspect the pilot light regularly. That way, you’ll keep cold air away!

Inspect the Pilot Light

Inspecting the flame is critical to ensure your furnace is working properly. Weak or no flame could result in cold air blowing from the furnace. Here’s a step-by-step guide:

  • Find the access panel on the furnace and remove it.
  • Set the thermostat to “heat” and turn up the temperature.
  • Look through the small window on the furnace’s burner cover for the pilot light.
  • Check for a blue flame. 
  • If it’s yellow or flickering, there’s an issue.
  • Follow manufacturer instructions or call a pro if any issues are found.

It’s important to inspect gas and electric furnaces before starting them after a long period of non-use.

Regularly check other areas that could cause heating problems, e.g. ductwork, filters, fan blades, and electrical connections. A damaged part might block hot air from flowing. Suggestion include

  • Change or clean air filters every couple of months.
  • Dirty ones can block airflow and stop heating elements from working properly. 
  • Don’t place flammable materials near the furnace as they’re a fire hazard. 
  • Have a professional inspection at least once a year. 
  • This reduces breakdowns and keeps you safe from carbon monoxide poisoning.

By following these guidelines and checking the pilot light, your furnace will run efficiently and keep you warm in the winter. So why cuddle with a blanket when you can snuggle up with your thermostat?

Adjust the Thermostat Settings Of the Furnace

Make sure your home’s temperature settings match your desired comfort level. 

  • Keep an eye out for dust or debris on the thermostat and clear it away. 
  • Set up your HVAC system correctly according to the manufacturer’s instructions. 
  • Check the wiring and replace any dead batteries. 
  • Investigate if the circuit breaker has tripped and reset it if need be.

It’s essential to ensure the filter is clean and replaced regularly. A blocked filter affects your furnace’s performance, so replace filters every few months. For extra energy savings, invest in a programmable thermostat. It’ll keep your home warm at specific intervals. 

Don’t blame the furnace for blowing cold air – it’s just gasping for breath!

Check the Gas Supply Of the Furnace

It is very important to check the gas supply for your furnace to work correctly. Make sure the valve is in the “ON” position. If it isn’t connected, attach it and test your furnace until heat is produced. If it doesn’t work, see if any other gas appliances are working properly. If not, call an expert.

Cold air from your furnace could also be caused by inadequate or malfunctioning gas pressure. Check the main valve and make sure it’s completely open. Be careful when making adjustments as this can affect pressure delivery.

When installing a new system, check for leaks that could cause damage or even explosions. Faulty installations can also cause problems – inspect this and other steps to fix the issue.

Give your furnace’s flame sensor some attention and it should start producing heat.

Clean the Flame Sensor Of the Furnace

To get your furnace running efficiently, cleaning the flame sensor is key. Clear any dust, debris, or soot buildup to ensure the readings are correct.

  • Find the flame sensor: it’s near the pilot light and looks like a thin metal rod.
  • Unfasten and pull it out using a screwdriver.
  • Lightly sand both ends until they are shiny.

Be aware, improper cleaning or too much exposure can harm the flame sensor’s function, resulting in cold air from the furnace. Also, clean intake filters, ducts, and other furnace parts. A dirty flame sensor can cause bad control signals and the furnace to shut down; get help from a pro if you’re not sure.

Beforehand, switch off electrical appliances, and have tools like pliers and wire cutters ready. Some furnaces have live wires, so be careful when working on them. Keeping parts clean and doing regular checks will make your furnace more efficient and save you money on repairs. Test the limit switch for a reality TV show feel!

Test the Limit Switch Of the Furnace

To test the furnace limit switch, here is what to do:

  • Turn off the power at the breaker box.
  • Locate the switch near the blower motor or heat exchanger.
  • Detach the cover panel and remove the screws.
  • Use a multimeter set to continuity mode and test each side of the limit switch when it is in a closed position. 
  • A reading above infinity means there is sufficient continuity.
  • Reattach the cover and turn on the power.
  • Keep an eye out for overheating parts, such as bad wiring, dirty filters, or faulty thermostats.
  • Furnaces can be complex, so if unsure, call a furnace repair company. Improper repairs can make issues worse and may void any warranty.
  • Inspection can help prevent problems with heating systems.

Ignition Inspection and Reset Of Furnace

Checking and resetting the furnace’s ignition is necessary when investigating cold air coming from the furnace. Follow these steps to inspect and reset it:

  1. Switch off the power to the furnace
  2. Take off the furnace cover and find the ignition module
  3. Check for any loose wires or connections, and tighten if needed
  4. Reset the ignition module by switching off the power switch, and wait five minutes before switching it back on
  5. Restart the furnace and see if it produces hot air

Remember, not all furnaces have an ignition module. Read your manufacturer’s manual or talk to a professional technician before attempting any DIY troubleshooting. If after resetting the ignition, your furnace still blows cold air, other problems may be causing this. 

For instance, a filthy filter or a broken blower motor can also cause inadequate heating. It’s best to tackle each potential issue one at a time, instead of making assumptions without diagnosing them properly.

To make sure you get proper heating, change dirty filters often, check for obstructions in vents or ducts, and have regular maintenance appointments with a qualified technician.

Safety Measures to Consider When Troubleshooting Furnace Blowing Cold Air

To ensure your safety when troubleshooting why your furnace is blowing cold air, you need to take proper precautionary measures. In this next section, three sub-sections will be discussed that will help you understand how to maintain safety while troubleshooting – turn off the power, check for carbon monoxide, and don’t overwork your furnace when troubleshooting.

Turn Off the Power

When trying to fix a furnace that blows cold air, it is important to be careful. 

  • To turn off the furnace’s power, locate the circuit breaker panel and find the breaker that controls the furnace. 
  • Switch it off by turning it in a clockwise direction. If unsure, turn off all power going into the house. 
  • Check if there is still voltage running through the system before doing any repairs. 
  • Put signs near the breaker box or equipment warning people that repairs are being done to the heating system. 
  • When done, restore power supply back to initial state by following similar steps.

Beware that mishandling switches or even a small particle can put you in danger while fixing the heating system. Wear electrical gloves and use other protective gear such as goggles and boots. Check for carbon monoxide before the furnace becomes a problem.

Check for Carbon Monoxide Leak

Safety is of utmost importance when fixing a furnace blowing cold air. Carbon monoxide gas is invisible, odourless and tasteless, yet it can cause headaches, nausea or even death if inhaled in large quantities.

It is wise to install carbon monoxide detectors in each room of the house, so that you will be alerted before it’s too late. If you experience signs of carbon monoxide poisoning, such as shortness of breath or dizziness, immediately leave your home and call for help from a safe distance.

Also, make sure to inspect the vents that supply heat to the house and clear them of dirt or debris. In addition, maintain your heating system regularly by changing air filters and insulating pipes and ducts in attics and crawl spaces for proper ventilation.

For best results, consult certified HVAC professionals for installing carbon monoxide detectors or getting periodic servicing done on your heating system. Lastly, don’t try to push your furnace beyond its limits while troubleshooting.

Don’t Overwork the Furnace during Troubleshooting

  • Check the thermostat settings and make sure they’re right. 
  • Then, inspect the air filters. 
  • Dirty ones can block the airflow and mess with your home’s heating. 
  • Open any closed or blocked vents in your house.

If it’s all good after that, look for faulty sensors or electric ignition issues. But don’t get too deep if you don’t know what you’re doing. Best to call a pro.

Poor maintenance of the furnace can cause costly repairs and dangerous carbon monoxide leaks. Professional servicing is key to keeping the furnace running properly and avoiding safety hazards. 

Don’t take chances, call an expert rather than tinkering if you’re unsure. When your furnace blows cold air, let the professionals take over!

When to Call a Professional for Help with Furnace Blowing Cold Air?

To troubleshoot your furnace blowing cold air with possible issues in the gas supply or heat exchanger, you might have tried DIY methods. But if it doesn’t work, here are the reasons you should call a professional: multiple attempts fail, furnace issues damage your home, the furnace is too old, the need for maintenance or cleaning, and seeking expert advice and estimates for replacement options.

Multiple DIY Troubleshooting Attempts Fail

Failed DIY furnace repairs? No problem! Here’s what to do. Check the thermostat – is it on ‘heat’ mode and set correctly? Inspect air filters – clean or replace if they’re dirty. Look for blocked vents, and check the pilot light – if it’s out, relight it. If these steps don’t work, call a pro.

Remember to get annual service from a qualified HVAC technician. Don’t neglect it or you could damage your system. An experienced technician solved a Des Moines homeowner’s heating system in no time during an ice storm. So, don’t fret if your DIY repairs don’t work – there’s help!

Furnace Issues Are Causing Damage to the Home

Homeowners can have many furnace problems that can cause destruction in their homes. They can come from improper installation, wrong sizing, or bad parts. In some cases, a broken furnace may release carbon monoxide into the living area, which is hazardous.

If you hear strange sounds, smell bad odors, or feel cold air instead of warm, call a technician right away for an inspection and repair. Ignoring these signs may lead to more damage and endanger your family.

Certain furnace issues may need a professional because of their complexity. For example, a damaged heat exchanger can’t be fixed without an expert. It is better to hire someone with the skill set and knowledge to manage complex mechanical issues safely.

According to the USFA, in 2018 heating equipment caused 48,000 reported home structure fires leading to 594 deaths. You know it’s time to replace your furnace when it’s older than your favorite socks.

Furnace Is Too Old to Function Efficiently

As furnaces age, their performance can start to dip. This affects their ability to heat properly. When a furnace is too old to work efficiently, it’s important to consider replacing it. An inefficient furnace can cause energy bills to skyrocket and even pose safety risks.

Age is a factor when it comes to furnaces. Older models are more likely to have issues like malfunctioning thermostats or damaged heat exchangers. Plus, they lack the energy-saving features of modern models. An older furnace may also generate carbon monoxide if it’s poorly maintained or develops a crack in its heat exchanger. This emphasizes the importance of regular inspections.

Replacing an old furnace with a new one that has better energy efficiency ratings can save property owners money on utility bills and reduce their carbon footprint. Contact a professional HVAC contractor to evaluate your furnace’s condition and decide if repair or replacement is necessary.

Don’t wait to take action when your furnace is inefficient. Get help from experts before costs escalate and maintenance neglect becomes irreversible. 

Remember, your furnace needs constant care and maintenance to stay happy!

Need for Professional Maintenance and Cleaning Of Furnace

Furnace maintenance and cleaning are essential for it to work properly. Not getting help can cause bigger troubles later. You should change the filter regularly and hire a technician to clean the furnace fully. This will remove dirt, debris and other bad stuff that may affect the air in your home. It also helps keep you safe from gas and electric hazards.

It’s best to have a professional check-up at least once a year. If you don’t, your energy bill may rise and the heating system may break down. Avoid repairs by scheduling regular inspections with pros.

According to Energy.gov, heat takes up 42% of household energy in the US. Maintenance and cleaning can save you 30% on energy bills and extend your furnace life. So, get pro advice and save yourself a thrill!

Seeking Professional Advice and Estimates for Replacement Options Of Furnace

When your furnace is blowing cold air, seek professional advice and estimates for replacement options. Experts can inspect your unit and recommend a cost-effective solution. They have a variety of models to suit your budget.

There’s no need to panic. Professionals can identify the problem, repair it, or recommend a replacement. Make use of warranties and maintenance plans, so an expensive bill can be avoided.

Before replacing, consider upfront and long-term costs, warranties, and installation rates. Compare warranties from different manufacturers for quality workmanship and reliable after-care service.

Be aware that poor installation by unqualified personnel can lead to failure and breakdowns soon after installation – resulting in expensive repairs/replacements. Neglecting furnace maintenance will result in cold air blowing in all the wrong places.

Importance of Regular Furnace Maintenance and Cleaning

To keep your heating system functioning at its best, regular maintenance and cleaning of your furnace is necessary. In order to achieve this, you must focus on changing furnace filters regularly, cleaning up air ducts and vents, cleaning the furnace blower, clearing drain lines and condensate, and regularly inspecting furnace components. Let’s take a closer look at these sub-sections to protect your heating system and keep your home warm and comfortable.

Changing Furnace Filters Regularly

Keeping your furnace filter clean is key for effective heating. Here are 3 things to know:

  • Dirt in the filter slows air flow and strains the unit. This reduces efficiency and increases energy bills.
  • Left uncleaned, it can become clogged with dirt and debris. This forces the furnace to work harder.
  • Regular changing helps keep dust and allergens from circulating in your air.

It’s important to maintain and clean your filter regularly. Or else you’ll get higher bills and worse air quality. Get a skilled technician to check your furnace annually. This helps spot potential issues before they become costly. Also, clean your air ducts and vents before dust bunnies move in!

Cleaning Up Air Ducts and Vents Of the Furnace

For safe, clean air in your home, it’s essential to service your HVAC system regularly. Cleaning up air ducts and vents is an important part of this. Here’s how:

Stepsvacuum cleaner, brush, screwdriver, and gloves.
Gather the tools:Remove the vents. Use a brush or vacuum to remove dirt, debris, dust.
Turn off the power.Remove the vents. Use brush or vacuum to remove dirt, debris, dust.
Clean the ducts with a vacuum or call a pro.Check for leaks in the ductwork and make sure it’s sealed properly. This conserves energy and reduces bills. Plus, it minimizes contaminants and improves air quality.

Schedule HVAC maintenance with an experienced technician twice a year – before summer and winter. A routine inspection helps spot early signs of wear and tear, so repairs can be done sooner. It also ensures safety, extends equipment life, and keeps your home comfortable.

Properly maintained HVAC systems are essential for healthy living conditions. They minimize exposure to allergens like dust mites and pollen, and keep indoor comfort levels high all year round. Don’t forget to service your furnace blower – unless you prefer a cold home!

Cleaning the Furnace Blower

Maintaining a Furnace Blower is important for a good heating system. Here’s how to do it:

  • Switch off the power supply – safety first! 
  • Unscrew the blower door and use a vacuum with a brush attachment to remove dust and debris.
  • Disconnect the fan blades, then clean with a damp cloth or soft-bristled brush. Put everything back in place when done.
  • Cleaning your furnace blower every six months is recommended.
  • Consider the dirt and usage patterns in your area to decide how often to clean it. 
  • Unclog the drain line to keep your furnace running smoothly.

Clearing Drain Lines and Condensate

Proper maintenance of heating systems is key to success & efficiency. This includes clearing the drain lines and condensate. Neglecting these components can lead to a clogged system causing extensive damage. Here’s what you need to know:

1Locate condensation lines.
2Turn off electricity.
3Carefully remove drain lines.
4Clear clogs and build-ups.
5Reassemble drain lines.

Clogged or poorly maintained drain lines can cause critical issues, such as flooding and water damage in your living space. Regular maintenance minimizes energy costs. Check-ups help identify issues early and prevent unseen damages.

For instance, not maintaining drain lines resulted in five thousand dollars worth of water damage. Lack of maintenance led to losses caused by negligence. Take caution or you may end up paying a heated price – literally!

Regular Inspection of Furnace Components

Regularly assessing and maintaining your furnace is essential. Ignoring it can lead to reduced efficiency, high energy bills, or even complete breakdowns. To extend the service life of your furnace, always follow the manufacturer’s suggested inspection for its specific model. Here’s a guide to help with regular maintenance:

  1. Turn off the power supply to avoid injury or damage.
  2. Examine all accessible parts for visible signs of damage or corrosion.
  3. Clean the inside and outside components with suitable brushes, tools, or vacuums.
  4. Lubricate moving parts such as blower motor bearings, pulleys and belts using approved oils.
  5. Replace air filters according to recommended timelines or conditions observed in the inspection.
  6. Check gas fittings or heat exchangers for any leaks if you detect an odd smell upon operation.

Don’t attempt repairs beyond cleaning if you’re not qualified. Hire licensed experts for corrective action on faulty parts. In addition to cleaning and inspection routines, effective air filtration and thorough duct cleaning can help maintain good indoor air quality. 

In 1905, Alice H. Parker from Morristown, New Jersey, invented an early version of a gas furnace that used a single central burner within a hollow chamber filled with cold air. This novel mechanism provided more warmth than traditional coal fireplaces while consuming less fuel due to increased combustion efficiency.

Remember to check if your furnace is actually turned on when troubleshooting a furnace blowing cold air.

Tips for Understanding and Troubleshooting Furnace Blowing Cold Air.

Troubleshooting a furnace that’s blowing cold air can be tricky. Here are some tips to help you figure out what’s wrong and get warm air flowing again in your home.

Step 1: Thermostat Settings

Make sure your thermostat is set to “heat” mode. And double-check that the temperature is higher than the current room temp. If needed, replace the batteries.

Step 2: Inspect Your Air Filter

A dirty filter can block the airflow, leading to cold air. Clean or replace it regularly.

Step 3: Other Issues

If Step 1 and 2 don’t help, there may be other causes like a malfunctioning pilot light, a dirty flame sensor, blocked ducts, restricted airflow, or clogged condensate lines.

It’s also a good idea to have a pro HVAC technician look at your heating system regularly. Moreover, use high-quality filters and make sure the fan settings are correct. Programmable thermostats and sealing drafts around windows and doors also help boost energy efficiency.

By following these tips, you can easily solve furnace-blowing cold air issues and enjoy warm air in your home!


A clogged air filter blocks out warm air, making the furnace blow cold. Change or clean filters regularly for optimum efficiency. Clogged Air Filter, Pilot Light Issues, Malfunctioning Thermostat, Lack of Gas Supply, Dirty Flame Sensor, Faulty Fan Limit Switch, and Ignition Problems are some of the potential reasons that could cause your furnace to blow cold air. According to Energy.gov, heat takes up 42% of household energy in the US. Maintenance and cleaning can save you 30% on energy bills and extend your furnace life. So, get pro advice and save yourself a thrill! Regularly assessing and maintaining your furnace is essential. Ignoring it can lead to reduced efficiency, high energy bills, or even complete breakdowns.