While some areas of the country can get by without a heater for most of the year, this isn’t the case for the majority of homeowners. Heaters are integral to a home’s comfort and safety during the frigid winter months when the temperatures outside begin to plummet. Not only does a heater keep the house warm and comfortable for the people and pets living there, but it also helps to prevent damage to the home’s systems, like the water lines that run throughout the house.

To ensure your heater continues to work at peak efficiency, it’s important to maintain it regularly and pay attention to any signs that indicate a problem. If you detect an issue with the heater, you should take action as soon as possible to repair it. Use this guide to discover 10 signs your heater isn’t working properly and how to fix each issue.

1. Inconsistent Indoor Temperatures

Heaters are supposed to warm the entire home to the temperature set on the thermostat, but if you notice your house frequently gets colder than the set temperature or that the temperature inside seems inconsistent throughout the day, this could indicate a problem with the appliance.

Start by checking to see if any of the vents are fully or partially blocked. A blockage could prevent the heater’s air from entering the home, causing temperature inconsistencies. If you notice any obstructions, clear the area to allow for proper airflow.

Next, check the air filter, especially if it hasn’t been replaced recently. A dirty filter can restrict airflow and reduce the appliance’s heating capabilities. You should also check the thermostat settings to ensure that they weren’t unintentionally set to a lower temperature than intended. If these methods do not work, you may need to call an HVAC technician for professional help.

2. Heater Is Blowing Cold Air

If the heater seems to be running, but there is only cold air coming from the vents, then you may have a problem with the pilot light, condensate line, ductwork, or air filter. Before you start to troubleshoot the issue, check the thermostat to verify it is on and set to the desired temperature.

Next, inspect the air filter and replace it if it has not been recently replaced. If this doesn’t resolve the problem, check the pilot light to ensure it is lit and the flame sensor is clean.

The issue could also be caused by a blockage or leaks in the ductwork. Inspect the ducts and clear any blockages or patch any leaks that you find to restore proper airflow for the heater. Finally, if the condensate drain line is clogged, it can cause the heater to malfunction and blow cold air. Clear any clogs you find in the condensate drain line to resolve the issue. Call an HVAC technician if these repairs don’t fix the problem.

3. Yellow Pilot Light

The pilot light for a furnace is supposed to burn blue, so if you notice that the flame on the pilot light seems to be yellow, this could indicate that the appliance has a carbon monoxide leak. This problem is incredibly serious and should be dealt with as soon as possible. Carbon monoxide is a highly poisonous gas that is odorless, colorless, and tasteless, so you can’t tell when you are inhaling it.

Homeowners should turn off the power and the gas supply to the furnace, then leave the home until a licensed HVAC technician inspects the heater. You may also need to call in your local gas provider to have them shut off the gas from the outside of the home until repairs can be made.

4. Increased Energy Bills

Inflation will naturally lead to a modest increase in your energy bills over the years, but if you notice the amount you pay to heat your home seems to be increasing faster than anticipated, it could indicate that the heater is not operating as well as it could. This increased cost could be the result of a clogged air filter or clogged vent, which would force the heater to work harder to heat the home. If this is the case, replace the filter and clean the vents to resolve the issue.

Another reason for increased heating bills is if there is a problem with the thermostat. This could cause the heater to cycle on and off unnecessarily, leading to a waste of energy. Homeowners can fix these issues by adjusting the thermostat settings or investing in a new one. Ultimately, the older a heater gets, the less efficient it will become, so if the heater is 15 to 25 years of age, it may be time to start saving for an upgrade.

5. Clogged Air Filter

The air filter for a furnace system should be replaced about once every 90 days, otherwise, the trapped hair, dirt, and other debris can clog the filter, reducing airflow and restricting the heating capabilities of the system. Filters will naturally become clogged over time, which can reduce the heater’s efficiency. So if you find that your heater isn’t blowing with the same force, the air is coming out colder than expected, or that heating seems inconsistent, then it’s recommended to check and replace the air filter to restore normal functionality. This is a problem that homeowners can handle without any professional help, allowing you to save on the cost of maintenance.

6. Uneven Heating Throughout the Home

Whole-home heating systems should heat the entire house equally, allowing the basement, the main floor, and the second floor to reach the same temperature set on the thermostat. If you notice that one or more rooms in your house are colder than the rest, the heating system may not be operating as effectively as possible.

Check the vents in each room to ensure they are not blocked and inspect the ducts for any signs of debris buildup that could be restricting the airflow into the room. You can also check and replace the air filter if you find that it is clogged with hair or debris. Alternatively, if the insulation for each room is too old, missing entirely, or poorly installed, this might be causing the temperature discrepancy. Hire an insulation professional to insulate the rooms properly to prevent unnecessary heat loss.

7. Heater Won’t Turn On

There is a clear problem that needs to be resolved if your heater simply won’t turn on, but before calling in HVAC pros to help solve the situation, there are a few easy things you could try. Start by checking that the thermostat is turned on and that it is on the heat setting. Also, check the temperature on the thermostat to make sure it is at the right level to heat the home.

Next, check the breaker switch for the heater. If the breaker is switched off, then the heater won’t be receiving any power, which in turn means that the electronic igniter will not work. Switch the breaker to the on position and check to see if the issue is resolved. If this does not work, then the issue may be the gas supply. Check the gas supply in the home by testing other gas-using appliances.

If the gas seems to be operating properly, then you should inspect the ignition system to see if the pilot light is igniting. Another issue could be a clogged air filter, which can prevent your heater from turning on due to restricted airflow. If the air filter has not been recently switched, then take the opportunity to replace it. If the heater still won’t turn on, then you will need to call an HVAC professional to inspect and repair the heater.

8. Thermostat Malfunctions

A malfunctioning thermostat can cause a lot of issues when it comes to heating the home. Begin by ensuring that the thermostat is turned on and that it is either set to heat or auto, depending on the model. If the thermostat is set to cool, then it will not trigger the heater to turn on. Additionally, you should replace the old batteries in the thermostat with a fresh set.

Once you have checked these basic settings, the next step is to make sure the heating schedule is correct based on your desired comfort level. Sometimes the issue can be as simple as switching the programming on the thermostat to heat the home to the optimal temperatures throughout the day and night. However, if the thermostat issues persist, it might be best to replace the old thermostat with a new model.

9. Heater Won’t Ignite

A gas heating system will typically have an electronic ignition that lights the pilot light, which in turn lights the main flame to generate heat. If the heater is not igniting, then it will be unable to produce heat for the home. A pilot light might go out due to something as simple as a draft, or it could be a result of a tripped fail-safe inside the furnace.

Open the access panel on the furnace and locate the pilot light assembly reset switch. Turn it to the off setting and wait about 5 to 10 minutes for any excess gas to dissipate, then turn the switch to pilot to trigger the flow of gas. Hold the reset button or use a long match to relight the pilot light.

If the issue is caused by a dirty igniter, you should turn off the power and gas supply, open the access panel to the burner compartment, and find the igniter components. Then, use compressed air to dust off the ignitors and put the panel back in place. Lastly, restore power and the gas supply to the heater. If this does not work, you might need an HVAC professional to inspect and repair the problem.

10. Heater Shuts Down Intermittently

Most heating systems are designed to come on when the temperature inside the home is below the set temperature on the thermostat, but if you find that the heater is turning off at odd intervals, this could point to an issue with the flame sensor. The flame sensor is a safety device that detects when a flame is present while gas flows through the system and automatically shuts down the heater if it does not sense a flame.

A dirty flame sensor could lead to false readings, causing the heater to shut down intermittently. You can fix this problem by turning off the power and gas supply to the heater and opening the access panel to clean the flame sensor. Use light grit sandpaper to remove carbon and soot buildup, then follow with compressed air to get rid of any residual debris before closing the panel and turning on the power and gas supply. Contact an HVAC professional if the issue persists.