A furnace is one of the essential things in your home during the winter season, so your home’s comfort relies heavily on your furnace in cold weather. But when it’s not giving off enough heat, it can quickly make your home a miserable one. You might be wondering why your furnace is not heating your house; it could be as simple as a dirty air filter, or it could be a more serious issue like a faulty ignition system or a cracked heat exchanger.
There could be a couple of reasons why your furnace isn’t heating your home. Just a few simple things to check before you write the furnace off as a goner.
The filter acts as a barrier, and when it’s filled with dust, dirt, or other particles, it can impede the flow of air. When airflow gets restricted like this, the system can overheat and shut itself off as a safety measure.
Heat also will not get into rooms if supply vents are blocked or closed. Just be sure furniture, curtains, rugs, and the like aren’t blocking up your vents.
Additional causes include a bad blower motor, ignition issues, a soiled burner, defective limit switch, or problems with the fuel supply.
Why does My Furnace Blow Cold Air?
Having your furnace on but the air coming from it is cold is one of the most aggravating furnace issues you can experience. It’s not unusual to be wondering, “Why is the air coming out of my furnace cold?” and there are a few reasons for that.
Look at your thermostat first. Make sure it’s set to Heat, and check whether the fan is set to On instead of Auto — if it’s set to On, the fan will keep running even when the furnace itself isn’t heating, so the air coming from the ductwork can feel cool.
A dirty air filter can also be the culprit. Since the filter covers the airflow path, a clogged one restricts airflow, and that restriction can cause the system to overheat, which then trips the limit switch and shuts off the burners (but not the blower).
Both ignition and gas flow problems can cause the burners not to get hot in a gas furnace. That is usually the result of a dirty flame sensor; the flame would come on, then go off, then lock out. However, when your furnace is blowing cold air more than warm air, it’s time to call an HVAC tech — not get into the habit of trying to jump-start it by turning it off and on repeatedly.
Why Is My Furnace Not Running?
If your furnace is dead and you have turned up the temperature on your thermostat, but nothing is happening, then you are most likely thinking to yourself, “My furnace won’t turn on!” Begin with the simple things.
Verify if the thermostat is powered and is the correct one. Replace the batteries if necessary. Next, peek in your breaker panel for a breaker that’s tripped. A service switch may be located on or near the furnace, and it may look similar to a standard light switch. Check to be really sure it wasn’t just accidentally switched off.
For a gas furnace:
Is the gas being shut off to the house? Never try to work on gas lines or furnace gas elements yourself.
A clogged filter, bad thermostat, bad control board, failing ignition component, safety switch, and others could all be the cause of your furnace not lighting.
Once you have done your research and you still have a non-firing furnace, get it checked out by a pro.
Why Is My Furnace So Loud? Should I be concerned about this?
A gas furnace for the entire house will vibrate and hum on startup and while operating. When you’re busy trying to figure out, “Is my furnace making a loud noise?!” — write down the type of noises and the timing of the noise: can you hear it during startup, while running, or stopping?
It may be that the cover, a screw, or another part has come loose. Thumping noises may be caused by a late ignition in a furnace.
A squeal or screech sound could be the blower belt, the blower motor, or the blower bearings. Grinding sounds may also indicate other mechanical issues that necessitate immediate attention.
Never dismiss a new or louder furnace noise. Running a gas furnace with a mechanical problem could let that problem get worse. If you hear a loud bang, grinding, or anything else unusual, turn it off and call a licensed HVAC technician to come out for a full assessment.
Why Does My HVAC Smell Like It’s Burning?
There are a couple of different reasons why you may be getting a burning smell from your furnace. You are most likely thinking to yourself, “Why does my furnace smell like burning?” because you are smelling it as you power up the furnace for the first time after it has been sitting for a while.
The dust that has settled inside the system over this time gets heated, and that’s what you’re smelling — a bit like the system cleaning itself out as it warms up. This smell usually fades on its own after a short while. But you also have a valid reason to be concerned if you smell something burning, or there’s an electrical smell in your home. It could be an overheated motor, an electrical part, a wiring problem, or a mechanical malfunction.
If you feel heat or smell burning plastic, or see smoke, shut off your furnace and call a pro. If smoke or fire breaks out, get everyone out of the house immediately and call 911 or your local fire department.
Check the furnace air filter.
When a filter is clogged, its effect on airflow can be very similar to closing a vent, so the airflow across the furnace heat exchanger is reduced, causing the heat exchanger to get hotter. Dirty, clogged filters make your furnace work harder, lead to less efficient heating, shorten run times, use more energy, and potentially shut the system down or cause it to overheat.
If you use a washable filter, rinse it under water according to the manufacturer’s instructions, and check it regularly. If you use a disposable filter, change it as per the manufacturer’s recommendations. If you have pets, smokers, construction dust, or heavy dust in your home, you may need to change filters more often. Before installing a new filter, make sure it’s the correct size and type specified by your furnace manufacturer. (For general guidance on filter maintenance and home heating efficiency, the U.S. Department of Energy offers helpful resources.)
When Should You Call an HVAC Professional?
Furnace troubleshooting that a homeowner can attempt on their own includes thermostat inspection, filter replacement, and ensuring that the vents are not obstructed. Gas line repairs, electrical connections, burner maintenance, ignition issues, and control problems should be left to professionals.
An HVAC company should be called in when the furnace is short-cycling, meaning it repeatedly turns off and on. You should also call one if the furnace is making strange noises, emitting a burning odor, not producing enough heat, or showing several other signs of improper functioning.
HVAC repair services usually address minor problems that may arise in a furnace and fix them before they escalate into expensive and complicated repairs.
Final Thoughts
When you start wondering, “Why is my furnace not heating my house?” — the thermostat, the filter, the power supply, and blocked vents are usually the culprits behind the heating issues. Luckily, restoring proper airflow and inspecting these components can often fix the issue.
On the other hand, if the furnace is giving off cold air, making noises, giving off burning smells, or failing to turn on, the wisest choice would be to contact a professional technician for a more thorough inspection.
Regular furnace maintenance, frequent air filter replacements, and good troubleshooting habits can make a noticeable difference in your heating system’s efficiency and considerably improve your quality of life during the heating season.
FAQs
When should you service a furnace?
At a minimum, a professional cleaning and inspection of your furnace should be done once a year. Components can be replaced, energy efficiency can be improved, and unexpected breakdowns can be avoided through preventive maintenance.
How do I make my furnace work better?
Keep your filters clean, keep vents unobstructed, seal air leaks around windows and doors, and make sure your house is properly insulated. Regular furnace maintenance can also increase efficiency.
How long does a furnace last?
A properly maintained furnace will last 15 to 20 years. Keep in mind the life expectancy depends on furnace type, quality of installation, use, and maintenance.
Does a heater work harder with a dirty filter?
Yes, a dirty filter impedes airflow in the furnace, causing it to work harder to heat the house. Changing your filter often can help increase efficiency and airflow.
Should I replace or repair my old furnace?
It depends a lot on how old the furnace is, how much it will cost to repair, how efficient the furnace is, and what type of furnace it is. If a gas model with frequent, expensive repairs is approaching the end of its life, it may be better to invest in a modern, energy-efficient model.
