Is Your Furnace On But No Heat Being Produced? Here's How to Fix it

It can be incredibly frustrating when your furnace is running but failing to keep your home warm. Despite seeing that your furnace is turned on, the vents still blow cold air and you shiver inside an uncomfortably chilly house. Before cranking up the thermostat or resorting to space heaters for warmth, it's important to troubleshoot what exactly is causing your furnace to not produce heat.

In many cases, insufficient heat from your furnace is caused by relatively minor issues that you can often address yourself without needing professional HVAC technician assistance right away. From examining common components like the air filter and flames to inspecting the furnace's electrical parts, taking the time to methodically check everything can get your heater flowing hot air once again.

Signs Your Furnace Is On But Not Heating Properly

How do you know if your furnace just isn't keeping up with heating demands versus having an underlying issue causing it to not produce heat at all? Here are some telltale signs your system has a specific problem prohibiting it from warming your home effectively:

• The furnace is blowing cold instead of hot air
• You've turned up your thermostat but the house still feels chilly
• Your gas or electric furnace keeps running nearly continuously but the temperature doesn't rise
• You hear the furnace running louder and longer than usual between heating cycles
• Rooms farthest from your furnace feel colder than ones closer to it

While an older furnace may indeed struggle to meet peak heating loads, like when outside temps become extremely cold, if you're seeing one or more of the above issues, that likely signals a performance problem worth investigating.

Furnace Running Harder to Overcome Issue

Why might your furnace run harder and longer while still failing to sufficiently warm your home? When components responsible for producing and distributing heat aren't working right, the system has to work overtime unsuccessfully trying to compensate for where it's lacking.

Much like how a dirty air filter causes your furnace blower to work harder to push air through congested ventilation --issues with flames, airflow paths or electrical parts can force it to run excessively long without achieving desired temperatures.

Inspect and Change Your Furnace Air Filter

One of the easiest things to check and remedy is the condition of your furnace air filter. This component is responsible for trapping dust and particles as air from your home's return vents passes through your heating system on the way back out to individual room supply registers. When clogged with debris, airflow becomes greatly obstructed, preventing warm air from circulating properly. This forces your furnace to run harder and longer trying to warm your living spaces.

How Often to Change Filter

Many HVAC professionals recommend changing your furnace filter at least every 30-90 days when your system is in use for heating and cooling. During peak operating seasons or in homes with pets that shed more dander and hair, opt for 30 day filter changes.

To inspect your furnace filter, first turn off power to your heating system at either the thermostat or typically via a panel switch. Then open your furnace access door and locate the filter either before or after the blower component. Remove the dirty clogged filter and replace it with a new clean filter of the same dimensions. Securely return the access panel before restoring power and trying your furnace again.

Clear Any Airflow Obstructions

For warm air to effectively circulate out to living spaces, the distribution path along ductwork leading to and from your furnace must be unimpeded. Aside from the filter itself, look for other blockages that could limit airflow like:

• Close proximity furniture or stored items pressing on vents
• Closed interior air dampers to certain rooms
• Kinked flexible ductwork preventing air passage
• Debris accumulated inside floor and wall supply registers
• Exterior vent covers that become blocked with snow, ice, leaves, etc

In addition to clearing any visible flow obstructions, try opening vent louvers fully and redirecting them away from furniture or window furnishings. Ensure dampers are open to all rooms needing heat. Adjust the direction of adjustable side vents to point hot airflow deeper into the room's interior rather than just blowing along walls where it cools rapidly.

Inspect Furnace Blower Motor

The furnace blower circulates air across heated elements and out supply ducts during operation. If this fan is damaged or not spinning correctly it will limit normal airflow delivery through the system. Problems could range from loose, broken or missing fan blades to issues with the bearings or motor connected to the blower component itself.

Use a bright flashlight to visually inspect for debris or damage preventing the blower wheel from spinning smoothly. If blades or the motor itself feel tight or unusually noisy, it's important to call in an HVAC contractor for professional repair.

Check the Condensate Drain Line

High-efficiency furnaces as well as some others pull humidity out of circulating home air during heating cycles. This water produced condenses on internal cooling coils and drains away through a dedicated plastic condensate line leading to a floor drain or external point of discharge. Issues with this drain line can cause furnace operation problems like:

• Water backs up and overflows, triggering safety shutdowns
• Excess humidity reintroduced into heated air, reducing comfort

To inspect for drain blockages, check for water pooling around the base of your furnace. Follow the path of the drain line to see if any segments hold standing water or feel clogged upon squeezing with moderate pressure. Clear obstructions, then pour some distilled white vinegar down the length of the line to prevent further buildup.

Calling HVAC Professional for Repairs

In situations involving access to internal furnace components or diagnosing complex electrical issues, it's best to have a qualified heating and air conditioning contractor assess and complete repairs. Technicians have the expertise, tools and diagnostic capability to identify problems and restore full system performance.

Warning signs to call in a pro include the furnace repeatedly tripping off on safety devices, strange burning smells from the unit, carbon soot accumulating around vents and hearing unusual noises with component operation. Putting off needed fixes risks escalating problems.

Examine Thermostat Settings

Sometimes it's not a mechanical issue in the furnace causing insufficient heat but rather a problem with the thermostat settings controlling it instead. Ensure your programmable or smart thermostat is properly configured by checking:

• Thermostat set to "Heat" not "Cool"
• "FAN" set to "AUTO" for normal cycling
• Day and Time match actual
• Desired room temps entered correctly
• Hold/Vacation modes aren't overriding usual temps

During troubleshooting, bump up the heat setting 5-10 degrees temporarily. If this triggers noticeable hot airflow, you likely had the thermostat set too low all along. Be mindful of unintended setting changes if you adjusted things during diagnostic steps.

Press Reset Switch for Power Restart

Furnaces have a reset button or switch designed to cut off then restore power as a way to reboot normal operation if problems occur. Things like voltage fluctuations, electrical storms or routine on/off cycling can sometimes trigger a furnace to need a simple power reset before working again. Locate the red reset button near your furnace's burner assembly and press firmly for 1 full second to cycle electrical power.

Caution: If you find yourself needing to hit reset very frequently in order for your furnace to produce heat, that likely signals an underlying operational problem requiring professional assessment and repairs.

Catching and fixing minor furnace problems now safeguards against escalation into more expensive breakdowns down the road. You can help ensure your heating system continues operating reliably by:

• Replacing air filters monthly
• Arranging yearly maintenance tune-ups
• Having a reputable HVAC company assess unusual noises
• Not delaying necessary component repairs

Looking out for early signs of insufficient heat like frequently clogged filters, increased operating noise or the system short cycling on and off excessively empowers you to address small issues before they snowball into costlier headaches later.

Investing a little preventative effort into properly maintaining your furnace avoids lots of frustration and expense when you need to rely on it heating your home the most. Reach out to your HVAC technician with any questions keeping your system running efficiently year after year.