HVAC Repair Tips


If your furnace is not blowing hot air, you would want quick ways to fix this problem. Although your best bet is to get a fully functioning furnace is hiring an expert from one of the better HVAC companies, you can also inspect and apply some fixes yourself. Follow this guide.

Top Fixes For A Furnace That’s Not Heating

Double Check Thermostat Settings

Considering that your furnace is turning on and still not heating, the first thing to check is the thermostat settings. You will be surprised to know that many people don’t check the thermostat settings when their furnace is misbehaving and, in the end, the culprit is changed settings.

So, check if someone lowered or increased the set temperature. If you have a programmable thermostat, you may have to check additional settings as well. Make sure that the fan setting is at “auto”. If it’s at “on”, the furnace will keep blowing air to the house even when its burner is not on. This will essentially allow cold or lukewarm air into the house from the vents.

Another trick is to change the temperature yourself and then set it back to the original and see if it wakes up your furnace.

Need more? Check the batteries of the thermostat and replace them. After that, set it up again and notice any difference.

Dirty Furnace Filter

A furnace air filter makes sure to stop contaminants and particles in the air from entering the system and vents. So, the air filter gets clogged with air particles and dust it stops. Therefore, you need to replace it often to allow only clean and fresh air into your house.

Moreover, a dirty air filter restricts airflow as well. This leads to poor airflow and your house not getting warm enough or reaching the set temperature. You will feel that your furnace is not heating your house when the actual reason will be the clogged air filter.

So, replace your furnace filter once every 3 months or earlier depending on your usage and the type of air filter. You should also keep in mind the instructions of the filter manufacturer about the frequency of the air filter replacement.

If you can’t decide when to change your furnace filter, look for signs like poor airflow, dusty indoor air, furnace running for longer time than usual, and more. However, it’s better not to wait for these signs and prepare a schedule for replacing the furnace filter.

Check The Fuel

If your furnace is turning on but not heating your house, it may have run out of oil or not receiving gas. When it doesn’t receive the fuel, the burners won’t turn on and heat won’t be produced.

If you have a gas furnace, check if your furnace is receiving gas or enough gas to light the burners. Find the location of the gas valve and make sure it’s completely on. Check other gas appliances to know if your gas supply line is working. Moreover, inspect the gas pipe connected to the furnace for damages or leaks.

For a propane or oil furnace, check the oil tank. There must be enough fuel for the furnace to work. If it doesn’t, have it refilled. If it does have enough fuel, the next step should be checking the pipes and valves for leaks. In case your oil consumption is increased suddenly, your oil tank or the pipes may be leaking. This will also affect your furnace and it won’t properly produce heat.

Obstructed Vents Or Registers

All vents and registers must be open for the furnace to operate well. If you have closed some vents, open them again. Moreover, check for furniture or anything else blocking the vents.

In case you notice low airflow from a specific vent, inspect it. It may be dirty or something might have fallen into the vent.

Check The Ignition System

There could be a problem with the ignition system of the furnace, which may be why it’s not heating your house.

Older furnaces have a pilot light that stays on. It allows the burner to turn on when the temperature drops. Check the pilot light if it’s still lit. If it extinguishes, the burners won’t light up even when they are required. So, if the pilot light is off, switch it back on and see if this also triggers the burners to turn on. For proper instructions on how to relight your furnace’s pilot light, read the user manual.

Most furnaces nowadays have an electrical ignition system. Make sure the furnace is receiving power. For a non-working ignition system that’s receiving power, you may need to clean the metal ignition strip because when it becomes dusty, it might not properly work. The strip is a delicate component so clean it gently. For instructions, use the owner’s manual or leave this to an expert.

Clean Or Replace The Flame Sensor

A flame sensor is a simple component that is responsible for allowing the gas valve to open only when the pilot light is on. If the pilot light goes off, it won’t allow gas into the furnace to avoid a gas leak.

A dirty or faulty flame sensor won’t work and the gas valve will remain open regardless of the fact that the pilot light is on or not. So, if the pilot light goes out, not only the furnace won’t heat, but natural gas will also leak into your house, which is highly dangerous.

A sign of a gas leak or a dirty/faulty flame sensor is that the gas odor will intensify as you go near the furnace.

You should try cleaning the flame sensor first. Turn off the furnace, remove the flame sensor, clean it, and then place it back. If the issue isn’t resolved, replace the flame sensor.

Inspect The Ductwork

We explained how closed or obstructed vents can affect the heating ability of your furnace. But when all the vents are open and the airflow in your house is still poor, there could be an issue with the ductwork. It could be dirty or leaky.

Inspecting the ductwork requires special skills and equipment so you should hire a professional to do this. They will also be able to suggest and carry out fixes if any dents or holes are found in the air ducts.

Make Sure Your Furnace’s Size Is Enough For Your House

If your new furnace is not blowing hot air, it could be nothing but the result of installing a wrong-sized furnace. A smaller furnace for a house will work continuously and might still not heat the house. Moreover, sometimes, small furnaces blow cold air because they can’t correctly read their internal temperature.

A furnace that is comparatively bigger for your house will also show problems. It will suddenly turn on and off, which can affect its performance and components.

So, have an expert determine whether your furnace’s size suits your house or not. If it doesn’t you will have no other option than to replace the furnace.


Many different problems can trigger your furnace to not heat the house. So, use the above-mentioned suggestions to identify the problem and fix it. For best results, hire furnace repair services Tysons Corner who will thoroughly inspect your furnace and perform repairs or replacements as required.


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