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Carrier Furnace Not Blowing Hot Air? 8 Common Causes (+ Fixes)

Your Carrier furnace might not be blowing hot air because it’s overheating, the pilot light is faulty, the thermostat is set too low, or the fan limit switch is faulty. You can get your furnace to blow hot air again by cleaning all parts, replacing broken ones, and setting a high temperature to maintain the comfort inside your home.

In this article, we’ll go over the most common reasons why a Carrier furnace isn’t blowing hot air. I’ll also discuss the appropriate fixes for each of these causes.

carrier furnace not blowing hot air

Common Issues And Their Identification

To perform DIY repairs, it is important to be equipped with the right information to identify the source of the issue. So, in this section, I will take you through the common issues that prevent your Carrier furnace from distributing the right heat around the house.

Ignitions Issues

The ignition process is very crucial in furnaces to start the heating process. If your furnace is not turning on or heating up, there might be an ignition problem. This can result from wear and tear due to aging or damage due to dust buildup. The igniter might be faulty and need a replacement.

Pay attention to abnormal sounds like clicking noises, or if the pilot light is tripped off repeated attempts to ignite, or simply a cold draft when your furnace should be turning up the heat.

Dirty Clogged Filters

Furnaces need clean air to function optimally. However, the dust and debris accumulation can result in clogged and dirty filters which can stifle the airflow and also result in your furnace leaking water.

Over time the filters end up trapping dust and residue that cause the furnace to overwork which can result in frequent pausing of your furnace. Reduced airflow, uneven heating, or an uptick in your electricity bill are the results. Check your filters regularly for visual cues.

Thermostat Complications

If the temperature on your thermostat is lower than the room temperature, there’s no reason for your Carrier furnace to generate hot air. Hence, sometimes your furnace must be working fine however the temperature instructions are given wrong by the thermostat. When the thermostat starts working abnormally it might reduce the heating or result in no heating at all.

This can result in temperature inconsistencies, unresponsive controls, or sudden heating halts. Test by setting the thermostat higher than the current room temperature. Also, check that your thermostat is updated.

Malfunctioning Blower Motor

The blower motor is the crucial component that pushes the warm air into your home. However, over time wear and tear can take a toll on the blower motor, impeding its ability to circulate warm air.

Check the blower motor, if you hear any unusual sounds like grinding or humming, notice weak airflow and chilly surroundings despite the furnace running.

Gas Supply Glitches

If your furnace runs on gas, any disruption in the gas supply can leave you in the cold sweat. This can be a risky situation if the right precautions are not taken. Issues with the gas line, valve, or pilot light can disrupt the fuel supply.

You can suspect a gas supply issue, if there is a lack of heat despite the furnace running, or if you notice a faint smell of gas. Check for visible gas leaks and verify the pilot light is on.

Faulty Fan Limit Switch

If you’ve ruled out other issues mentioned in the article, the fan limit switch might be the problem. The fan limit switch turns off the heat when temperatures get too high in the furnace. The switch will also cause the fan to stop blowing air into your ductwork.

If the fan limit switch is faulty, there’s a chance that it turns the furnace off at inappropriate times. This may happen randomly, or you may find that the device isn’t pushing out any air at all.

Faulty Pilot Light

Older Carrier furnaces use a pilot light for ignition. The pilot light needs to be lit for ignition to occur. If the pilot light goes out, it means there will be no flame to ignite the gas coming from the burners.

Multiple issues can affect the pilot light. Sometimes, you need to light it manually. Other times, it’s dirty or even broken. If the pilot light is causing an ignition issue, you need to remove it, inspect it, and take appropriate action based on your findings.

The Furnace Overheating

Your furnace is constantly generating heat through the burners. The burner flame allows air to be heated up, which is then blown into the ducts.

The furnace itself and your ductwork need to withstand this consistent heat — when things get too hot, problems can occur. A safety switch may trip in the furnace, causing the burner’s gas supply to shut off. 

There are a few reasons for overheating in a furnace, but a dirty air filter is the most common cause. The debris collected by the filter can block the airflow from the furnace toward the ducts, trapping the heat inside the furnace. This causes the internal temperature to rise and trip the safety switch.

Step-By-Step Troubleshooting Guide

Now, you can solve the issue once you identify the source of the trouble. In this section, I will take you through the guide to solving each problem for you to follow:

Ignition IssuesStep 1: Turn off the furnace’s power.
Step 2: Open the main compartment.
Step 3: Find the ignition sensor. The sensor is attached to a metal rod fastened to a hole in the combustion chamber.
Step 4: Remove the sensor.
Step 5: Clean the sensor using fine sandpaper and a microfiber cloth.
Step 6: While cleaning, check for cracks in the sensor. If there are cracks, it needs to be replaced. But if it seems to be in good condition, place it back after a thorough clean. 
Dirty Clogged FiltersStep 1: Turn off the furnace.
Step 2: Locate where the filters are situated in your furnace, which is typically near the air handler.
Step 3: Check if the filters are dirty or clogged. 
Step 4: Replace them following the manufacturer’s recommendations with compatible filters.
Thermostat ComplicationsStep 1: Take a look at the fan settings. There are three options, apart from ON and OFF, there’s an AUTO setting as well. If the fan is currently set to ON or OFF, switch it to AUTO. That’s because the fan will blow continuously if you set it to ON.
Step 2: Verify that the thermostat is set to the desired temperature and mode. Reset it to the desired setting if the current setting doesn’t match your needs.
Step 3: Use a separate thermostat to compare room temperature with the thermostat reading. Recalibrate if necessary.
Step 4: If your thermostat uses batteries, check and replace them. A low battery can cause communication issues.
Malfunctioning Blower MotorStep 1: Usuaual sounds indicated potential issues. If you hear abnormal noises, take a closer look.
Step 2: Turn off the furnace.
Step 3: Locate the blower motor. 
Step 4: Check for visible signs of damage or obstructions.
Step 5: If the motor seems faulty, it’s best to consult a professional for repairs or replacement,
Gas Supply GlitchesStep 1: Turn off your furnace at the breaker box.
Step 2: Open the main compartment of your furnace.
Step 3: Identify the gas supply line and follow it to find a small box attached to the pipe which is the gas valve. 
Step 4: See if the switch on the gas valve is open. If it isn’t, then flip it over.
Step 5: If the gas valve is already open, see if you can find any signs of damage, such as cracks, or bends, and replace accordingly.
Faulty Fan Limit SwitchStep 1: Turn off your furnace.
Step 2: Remove the front panel and locate the limit switch in the furnace. 
Step 3: Make sure it’s installed correctly and hasn’t become loose.
Step 4: If it seems secure, check for cracks, chips, or other signs of damage.
Step 5: If you notice damage, or if the switch simply won’t work, replace it.
Faulty Pilot LightStep 1: Switch the furnace off.
Step 2: Open the combustion chamber.
Step 3: Check for a build-up of debris on the pilot light. You may see some black residue from the flames and gases that pass through the area. 
Step 4: If you find debris on the pilot light, clean it thoroughly. If cleaning it doesn’t fix the issue, move on to the next step.
Step 5: Check for cracks and other signs of damage. If it’s damaged, remove and replace the pilot light.
Step 6: When buying a new pilot light, make sure you buy a compatible one. You can use the model number on your current pilot light to ensure you get the right replacement.
The Furnace OverheatingStep 1: Switch off the power to your furnace.
Step 2: Remove the front panel. 
Step 3: Remove the filter. 
Step 4: Clean the filter thoroughly. If you have a disposable filter, throw it out and replace it. 
Step 5: Make sure the replacement filter is fastened correctly. Put the furnace panel back on and switch the furnace on. 

Seek Professional Assistance


HVAC Professionals are equipped with expertise and tools to tackle complex furnace problems. Knowing when to bring in an expert can prevent you from further damage and extra expenses. Here is a list of instances when you must look for a professional:

  1. Gas Smells: A distinct smell of gas indicates a potential gas leak, which is a serious safety concern. Evacuate the premises and call the gas company or emergency services. Gas-related issues demand urgent professional attention.
  1. Electrical Issues: If you suspect problems with the furnace’s electrical components, handling components, handling it without expertise can lead to safety hazards. When you notice sparking, exposed wires, or any electrical malfunction, look for an expert immediately. Electrical issues are best left to a certified technician.
  1. Complex Repairs: For intricate problems involving major components like the blower motor, gas valve, or control board, a professional touch confirms accurate diagnosis and proper repair.
  1. Problems Continuing After Self-Repair: If your attempts to troubleshoot haven’t resolved the issue, retrying it multiple times can lead to further damage. If the problem persists or worsens after your initial troubleshooting efforts call a professional.
  1. Under Warranty: Attempting repairs on a furnace under warranty without enough expertise can void the warranty. Contact the manufacturer or the authorized service provider for assistance to address any issues with your furnace, if it is under warranty period.

Maintenance Tips


Here are some of the things that you should involve in your maintenance routine to maintain the longevity of your Carrier Furnace:

  • Check and replace the filters regularly, it’s recommended to clean the furnace filters monthly and replace them every 1-3 months depending on your usage and the type.
  • Clean the vents and air registers by wiping them down every few months.
  • Inspect and clean the blower motor as needed. Turn off the power, remove the panel, and gently clean the dust and debris.
  • Check and adjust the thermostat seasonally for adjustments. Replace batteries as needed.
  • Inspect the gas connection annually by applying soap and water solution to the connections. If bubbles form, there’s a leak.
  • Clear the furnace exhaust vents annually by removing any debris or nests that may have formed to confirm proper ventilation.


  • Alanna Greene

    Alanna is an avid traveler who lives in Michigan. In addition to writing for Temperature Master, he also sells crafts on Etsy and takes long walks through the forests near her home.

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