Why is my furnace running but not heating the house?

Author: Kellen Turner III  |  Last update: Tuesday, July 8, 2025

Clogged or Dirty Air Filters In such cases, the blower fan will continue running, but no warm air will be distributed throughout your home. Regularly replacing or cleaning your furnace filter is essential for proper furnace operation and improved indoor air quality.

Why is my furnace running but no heat?

If your furnace turns on but no heat is produced, there may be a problem with the fuel supply or the ignition system. If something is stopping your furnace from receiving gas, there is no fuel to combust so the furnace will not create any heat. The furnace turns on but no heat comes out.

Why is my furnace running but the house is cold?

If your furnace is blowing hot but your home is still cold, it may be a problem with your ductwork. You may have leaky or damaged ducts that are letting hot air escape and cold air in. Sometimes a damper in the system can get miss-adjusted or come loose, thereby inadvertently blocking or reducing airflow.

Why is my furnace not reaching set temperature?

Clean your Air Filters, Vents, and Ducts – A clogged air filter will struggle to meet the thermostat's set temperature since the dirt and debris buildup prevents air from circulating through the vents. And as airflow into living spaces drops, so do comfort levels.

Why is my furnace not kicking on for heat?

If your furnace won't kick on when you turn the thermostat up, it could be due to a variety of reasons such as a tripped circuit breaker, a faulty thermostat, or a problem with the furnace itself like a malfunctioning igniter or gas valve. Checking these components might help you figure out the issue.

Furnace Not Blowing Hot Air - Easy Fix

Why is my furnace not heating my house up?

Furnace is not producing enough heat.

This may be caused by obstructed airflow or dirty or misaligned gas burners. In some cases, airflow is obstructed by a dirty furnace air filter, and if it is replaced, the problem is solved.

Why does my thermostat say heat on but no heat?

Possible reasons include thermostat issues (incorrect settings or dead batteries), power problems (tripped circuit breaker or blown fuse), and furnace malfunctions (dirty air filter, faulty ignition system, or tripped safety switches). Checking these areas can help identify the issue.

Why is my house not warming up with heating on?

If your home isn't warming up as expected, a dirty air filter, blocked vents, or thermostat issues might be to blame. Check and address these issues before considering professional assistance.

Why is my furnace not blowing as hot as it should?

Troubleshooting Tips For Furnaces Not Blowing Hot Air

Inspect your thermostat's fan settings to see whether they're “auto” rather than “on”. Ensure your thermostat has not been set to a lower setting by someone else. Check your thermostat's batteries and replace any that are exhausted or defective.

Why is my heating not reaching temperature?

Radiators might not be getting hot due to trapped air requiring bleeding, a malfunctioning boiler or central heating pump, thermostatic radiator valves that might be stuck or set too low, or the central heating system having sludge or rust which causes blockages.

Why is my house cold even with heating on?

This problem often points to inadequate circulation of warm air. It could be due to blocked vents, a failing HVAC fan, or issues with the furnace itself. Ensure that furniture or drapes are not blocking your vents. Also, check if your furnace's filter is clean, as a dirty filter can restrict airflow.

What to check if heat is not working?

5 Areas To Troubleshoot If Your Heater Is Not Working
  1. Wrong Thermostat Setting. Whether you have a SMART, programmable, or standard thermostat, it requires attention as you transition from hot weather to cold. ...
  2. Power Source Issues. ...
  3. Clogged Air Filters. ...
  4. Full Condensation Pan. ...
  5. Overloaded Motor.

Why is my furnace on but my house is cold?

The issue could be as simple as an incorrectly set thermostat, so always double check the settings. A more serious problem is a miscalibrated thermostat (it's sensing the wrong temperatures and shutting the furnace off early) or one that has a bad connection to the control board in the HVAC system.

Why is there no heat coming out of my vents?

While furnaces can stop operating for complicated reasons, home owners should check a few usual suspects first behind a lack of hot blowing air: Electrical problems causing a loss of power. Blocked air vents and ducts restricting airflow. Improperly configured thermostat settings.

How do I know if my thermostat is bad?

7 Ways to Tell Your Thermostat Is Broken
  1. The Thermostat Has No Power. ...
  2. The AC or Furnace Won't Turn On. ...
  3. The Heater or AC Won't Turn Off. ...
  4. The Thermostat Reading Doesn't Match the Room Temperature. ...
  5. The Thermostat Doesn't Respond. ...
  6. The HVAC System Is Short Cycling. ...
  7. The Thermostat Forgets Programmed Settings.

Why does my furnace turn on but no heat?

This can occur if there's a malfunction in the furnace's components, such as a faulty limit switch or a blocked heat exchanger. In such cases, it's crucial to consult a professional HVAC technician for a thorough inspection and necessary repairs.

Why is cold air blowing when the heat is on?

You Have Cold Air Blowing Out The Vents When The Heat Is On Because of a Dirty Air Filter. Hiding in the filter of your heating system is dirt and debris. If you aren't cleaning it regularly, this will accumulate over time, leading to problems with your heating system's efficiency.

Why is my furnace not heating but the fan running?

If no heat is coming off the vents even when the furnace's blower is on, it could be due to wrong thermostat settings. In this case, you should ensure the thermostat isn't set to cool instead of heat. This sounds simple, but it's a pretty common mistake. The fan constantly runs when it's turned on.

What would cause my heat not to kick on?

If your heater doesn't start, chances are the problem stems from having a dirty furnace. Having dirt on your blower motor or flamer sensor could render your furnace unable to perform. When the blower motor is too dirty, it won't pass enough cool air to the heat exchanger, leading to equipment failure.

Why do I feel so cold when the heating is on?

Poor circulation

Underlying arterial disease could be causing inadequate blood circulation, making it hard to maintain core body temperature, especially in your extremities. Smoking affects temperature regulation in a similar way by causing blood vessels to constrict.

Why is my furnace not keeping the house warm?

Check the air filter first

If the filter is heavily clogged with dust and debris, it cuts down on airflow, which in turn means less heated air is getting around the house. Change the filter for a clean one if it's clogged, and continue to change it every 1 to 3 months while the furnace is running.

Why isn't my heat reaching temperature?

Some of the most common thermostat issues include:

The thermostat is broken, not properly level, or dusty. The thermostat needs to be recalibrated. There is loose wiring causing a thermostat issue.

How much is a new furnace?

Ask twenty professional HVAC contractors the question, “How Much Does A New Furnace Cost?” and you'll probably get the same answer... “It depends.” On average, the cost of a new furnace can range from $2,000 - $14,2001. However, factors like furnace efficiency, type, size, and much more can impact this range.

Why is my furnace making noise but no heat?

Most likely, your furnace is making a clicking noise and not providing heat because your furnace's spark igniter is trying to ignite your pilot light or burners but is failing to do so. In other words, there's an ignition system malfunction that needs to be fixed.

Previous article
What is R7 insulation used for?
Next article
Do Ninja air fryers use Teflon?