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12 Common Heater Problems & How to Fix Them

11 Common Heating Problems

Discovering that your furnace or heater is not working makes for an unpleasant surprise — especially if it happens the dead of winter.

Unfortunately, all heaters and furnaces need to be replaced eventually, but the good news is that some heating problems can be fixed without having to purchase a whole new system. We’ll highlight some of the most common heater problems and identify the best solutions to fix them, whether it’s repair or replacement.

You’ll find more information on the following common heating problems:

Image of Goodman forced air furnace

The Goodman GCSS920804CN 80,000 BTU, 92% AFUE Single-Stage Gas Furnace is an extremely efficient central heating powerhouse.

What Can Cause a Furnace to Stop Working?

We often hear the question why is my heater not working, and the truth is, there are many different possibilities. Furnaces are complex systems that require a good amount of maintenance. There are a lot of moving parts and pieces that could be contributing to the system not working properly. The air filter could be dirty, there could be a crack causing a leak, one of the many parts could be loose, worn down, or need to be replaced, or a number of other issues could arise.

Furnace maintenance should not be overlooked and is imperative to keeping the system running properly. If you’re starting to notice a lack of performance, get the system checked out right away.

Central Heating Problems

Also known as forced air furnaces, central heating systems distribute heat throughout your home through a series of ducts. That being said, sometimes furnace problems are the result of faulty ducts, a defective heater or both.

Problem: Heater is blowing cold air

If you’re wondering why your heater is blowing out cool air, the first thing you should do is check your thermostat and make sure it’s set to the correct temperature. Try kicking it up a notch to see if there’s a noticeable difference. Make sure it’s set to “auto” instead of “fan on” — otherwise, your fan will run without blowing any heat. If you’ve checked your thermostat and verified that it was indeed on the right setting, then your issue may be one of many, including:

  • Dirty air filter – Air filters become dirty over time and need to be cleaned or replaced — otherwise, dirt and debris can inhibit your furnace’s performance and cause it to blow cold air. Change your air filter and see if that fixes the problem.
  • Leaky ductwork – Leaky ductwork is a virtually invisible problem, but it can cost you if it’s not resolved. If you’re comfortable with it, go into your attic or crawl space to check for leaks by walking alongside your ductwork and feeling for any blowing air. Bring a lit stick of incense with you and hold it near your ducts; if the smoke starts to move, that’s a telltale sign you have a leak in that spot. Seal off any leaks and insulate your ducts accordingly.
  • Pilot light issues – Check your furnace pilot light and make sure it’s lit. If it won’t light, make sure gas is flowing to it — check the gas valve and verify that it’s turned on. If your gas valve is on and your pilot light still won’t light (or it lights but doesn’t stay lit), you’ll want to contact a professional to examine the issue.
  • Lack of fuel – Whether you have a gas, electric, or oil furnace, your system needs fuel to properly run. If you’re low on fuel — or if fuel is unable to effectively power your furnace — your heater will not work as well as it should.

If none of these seem to be the issue, you should contact an HVAC professional to examine your heating system more thoroughly.

Problem: Heater will not light/stay lit

If your furnace is newer, it may not have a pilot light. Rather, it most likely uses electronic ignition. These newer systems will have a flame system to make sure that gas isn’t flowing without the heater being on. Sometimes, these sensors get dirty and need to be replaced — be on the lookout for this issue when inspecting your furnace. Cleaning and replacing these sensors is an easy fix you can do yourself.  

Problem: Heater won’t shut off

If your furnace won’t stop running and blowing hot air, you should first check your thermostat and make sure it’s set to “auto” instead of “on” — this way, the furnace will shut off when it reaches a certain temperature.

If your heater still won’t stop running, your problem could be one of two issues:

  • Your thermostat is broken or miswired
  • Your furnace blower is malfunctioning

First, examine your thermostat’s wires to ensure everything is plugged in correctly. Next, reset your thermostat to factory settings and try running your system again. If this doesn’t resolve the issue, you may need to replace your thermostat.

If you replace your thermostat and your furnace continues to run, your problem could be the result of a blower issue. Contact your trusted heating professional immediately for further inspection.

Problem: Certain parts of the house are not heating

If your heater is unevenly distributing heat throughout your home, your issue could be attributed to two primary things: dirty air filters and inadequate ductwork. Check your air filters for dust and debris and change them accordingly.

If your air filters are clean, or if replacing them doesn’t resolve the issue, you may need to inspect your ducts for leaks. Should you find that your ducts need additional work, contact an HVAC professional for further inspection.

Problem: Controls are not working

If you’re unable to properly control your furnace, the problem most likely has to do with your thermostat. Again, make sure your thermostat is set to the correct temperature, then try replacing the batteries to see if that fixes the problem. If it doesn’t, reset the thermostat per your manufacturer’s instructions.

If resetting doesn’t resolve the issue, as a last resort, you can pop open your thermostat and examine the wiring to make sure it’s correct.

If none of these actions resolve your problem, you most likely need to buy a new thermostat.

Problem: Fan is not working

If your furnace’s fan isn’t working, check your thermostat and make sure it’s set to the correct setting. Then, check your air filters and make sure they’re not so dirty that airflow is restricted. Extremely dirty air filters can sometimes cause your fan to stop working altogether.

Next, check your circuit breakers and make sure they’re on. (Note: Only turn your breakers on once. Flipping them on and off repeatedly can cause a fire!)

If turning on your circuit breakers doesn’t fix the problem, you’ll want to call an HVAC professional to inspect your system, as you most likely have a more complex problem on your hands.

Problem: Mold in your furnace

Moisture buildup is oftentimes the result of poor insulation or inadequate ductwork, creating the perfect environment for mold to grow.

If you have mold in your furnace, you’ll want to hire a professional to clean your system and take the necessary steps to prevent mold from growing in the future. This includes making sure your ducts and crawl space are properly insulated and sealed to prevent moisture accumulation.

You’ll also want to have your HVAC specialist clean your ducts every few years for preventative maintenance. Regularly changing your air filters will also help keep your system as clean as possible.

Problem: Heater smells like burning

A burnt smell — or a heater that’s actually smoking — is a clear sign that something is wrong. If your furnace smells like burning, shut it off and unplug it immediately, as leaving your heater on can potentially be hazardous. However, an unpleasant smell can merely be a sign of a dirty air filter or dust buildup in the furnace. Try not to panic and take swift action immediately.

After unplugging your heater, inspect your system for dust or blockage and clean accordingly. You may also want to replace or clean your air filters for good measure.

If the problem persists, you should contact a professional to check your electrical components or chimney for blockage.

Problem: Furnace is Short Cycling

Short cycling is when the furnace turns on and then rapidly turns off. Short cycling can result in only portions of the areas you are heating to warm up. This can be caused by a variety of issues including:

  • Dirty filter
  • Oversized unit
  • Thermostat fault
  • Thermostat placement

Furnaces are designed to run and work best when they are on for at least 15 minutes at a time. Shorter runs can impact the heat exchanger overtime.

Image of Dimplex electric fireplace
The Dimplex BLF50 Synergy 50″ Wall-Mount Landscape Electric Firebox is a stunning LED fireplace that can be used with or without heat for year-round enjoyment.

Room Heating Issues

Whether you have an electric fireplace, an infrared or blue flame space heater or a wall mounted unit, room heater problems are easier (and usually less expensive!) to resolve compared to central heat systems. However, it’s oftentimes better to simply buy a new room heater rather than trying to fix it, as a seemingly simple repair can potentially cost you more in the long run.

Problem: Controls not working correctly

If your heater’s controls seem to be faulty, first unplug the unit and plug it back in to see if that resolves the issue.

Next, check the heater’s thermostat (if it has one) and make sure it’s set to the correct setting. Try resetting it to see if that fixes the problem. If not, there could be an internal wiring issue — unplug your heater, carefully pry open the thermostat and make sure all wires are connected correctly. Consult your owner’s manual for guidance if necessary.

If this doesn’t fix the issue, or if you have a room radiator instead of an electric or gas heater with a thermostat, contact your local HVAC professional for advice. Replacing your heater may end up costing you less than hiring someone to fix your heater, so it’s best to ask your trusted heating specialist for an estimate before making any decision.

Problem: Fan doesn’t work

If your heater’s fan isn’t working properly, try unplugging the unit and cleaning the fan of any dust or dirt, which can inhibit its ability to run. If this doesn’t seem to fix the issue, make sure all internal wires are connected correctly.

If your wiring appears to be correct, check your home’s electric box for a tripped circuit or a blown fuse. If everything looks good, your fan’s motor may be broken, in which case you’ll need a replacement part. Consult your owner’s manual for advice and information, including any information about a parts warranty.

Problem: Heater is blowing cold air

If your heater turns on but it’s blowing cold air, turn it off and check to make sure there’s nothing obstructing the blower.

If you clear any debris or blockage and the problem persists, you could have a faulty heating element. If this is the case, you’ll have to replace it with a part that has the same voltage and wattage. Depending on the type of heater you have, this repair may or may not make sense for you — compare the cost of replacing the part to replacing the heater entirely and see which is the best option financially for you.


In a nutshell, sometimes the cost and effort of a repair is just not worth it, and you may be better off replacing your heater or furnace altogether under certain circumstances. Therefore, it’s best to do a cost comparison to see which option is right for you.

For more complex repairs, it’s always wise to consult with a trusted HVAC specialist before attempting to tackle the work yourself. Your heating professional can also give you a quote for any sort of repair or replacement work to help you make your decision.

Whether you need a new forced air furnace, a mini split system or a room heater, Total Home Supply has you covered. Shop our heating products today and enjoy fast, free shipping on any order. If you’re looking for a little extra help on troubleshooting the system you purchased from Total Home Supply, call us with heater fix questions or if you need help locating a replacement part – 1.877.847.0050.

Mickey Luongo

Mickey is the resident heating and air conditioning expert with over 15 years of experience in the industry.

10 thoughts on “12 Common Heater Problems & How to Fix Them”

  1. Deedee Lewis says:

    Recently my furnace has been blowing out cold air and I have been having to relight the pilot a lot. Thanks to your tips I went and checked the fuel level, which I had never even thought of checking until reading your article, but I think the problem is a lot deeper than that. I guess the next step for me is to contact an HVAC repair company and have them take a look at it.

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  3. Hi,
    I have braemer gas ducted heater (about 10 years ) Had a service guy who came out last week to clean the ducted heater. After cleaning for an hour my ducted heater isn’t working anymore. The heater runs for about 15 mins then stops (display panel shows reset). After resetting , it runs for around 10mins. Then the flames goes on and off every 3 second. He has changed the ingite sensor and some white cable sensor. But we it’s still showing error code 7 ( gas locked out). In between his cleaning process he had to cut the air vent silver tube underneath the house. If he didn’t joint /sealed it back properly , could this be the caused ? Thanks in advance.

  4. My Evidure port gas heater takes “ages ” to light up when pressing the ignition button. Is this a simple repair ? Thanks.

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