My Furnace Turns On But No Heat – Why?

homeowner feeling chilly due to furnace turning on but no heat

When it’s cold outside, you retreat into your home for warmth. You turn the furnace on and wait for the air to heat up. This reliable system works like a charm most of the time, but what if it behaves differently? What if the heating system turns on yet you do not feel hot air coming out of the vents? This situation is not uncommon. Many get frustrated when it happens, especially if the temperature is dropping fast. However, it is best to keep a level head and examine the potential causes one by one. Keep reading to find out what to do when furnace turns on but no heat.

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My Furnace Turns On But No Heat – Why?

The fact that the furnace turns on is a good sign. It means that the power system is probably fine but something else in the chain is preventing it from working as expected. The problem may turn out to be a simple oversight, in which case a few tweaks is all it takes to produce heat once again. This is true in most situations so there is no reason to panic. If the problem proves to be more complex than a regular homeowner can handle, then the best bet is to ask licensed technicians to take over.

In this article, we discuss three of the most common reasons why a furnace turns on without generating heat. These include incorrect thermostat settings, airflow problems, inadequate furnace fuel, and ignition problems. We will explain how things can go wrong for each of these. We will show how people might perform basic troubleshooting. These are easy tasks that anyone can do. With any luck, the furnace will immediately spring to life and the case can be closed. If it remains unresponsive, then do not attempt to go any further. Call for professional assistance. Learn from the experience and apply the lessons to prevent a recurrence.


image of homeowner adjusting programmable thermostat

A furnace is a machine that is designed to perform as instructed. If your intention and instructions are different, then you may get odd results. The thermostat functions as the control center of the entire system so make sure to feed it with the right information. For example, you may be expecting the furnace to produce hot air but the thermostat is not set to do this. In this scenario, there is actually nothing wrong with the equipment. It’s just that the settings need to be changed to get what you want. Maybe the thermostat is set to cool so you have to set it to heat. Someone could have tinkered with the settings when you were away. Never assume. Always check the basics.

Look into the fan settings. A lot of people think that a moving fan indicates that the furnace should be producing heat but that is not always true. If it is turned ON, then it will run nonstop regardless of whether there is a heating cycle or not. You will need to set the fan to AUTO so that it will only spin in tandem with a heating cycle. This is how you ensure that it blows hot air through the vents, and performs more efficiently. You can also change the temperature setting to a higher number. Try going 5 to 10 degrees up and see if that makes a difference. If you are still getting cold air from the furnace, then it is time to call the pros.

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HVAC Airflow Problems

Air needs to flow smoothly across the system in order for the furnace to function well. If there is an airflow problem, then heat may not be able to move from the source to the various rooms. One of the reasons why no heat is coming out of the furnace is that there is an obstruction along the air’s path. The following are the most common culprits in this scenario:

1. Dirty Air Filters

image of a dirty furnace filter

HVAC air filters are essential in improving air quality blocking dust, pollen, pet dander, and other unwanted airborne particles. These static filters prevent the furnace and the ducts from getting dirty but they are the ones that suffer in the process. After a while, their surfaces can get filled with a thick layer of dirt that prevents air from passing through. Homeowners should make it a point to check this every month and replace it whenever necessary. Stick to the manufacturer’s suggested replacement schedule or do it more frequently if you live in a dusty area with lots of pets.

2. Closed HVAC Vents

image of a homeowner placing hands in front of hvac air vent to check for airflow

The problem could be as simple as closed vents. See if the louvers are open and adjust when needed. Sometimes they could get stuck so try to take out the vent cover for cleaning. If these are still jammed, then you might have to replace the cover. You should also check whether there are things blocking the vents and registers. Perhaps someone rearranged the furniture and closed these off. Put things back to their original positions to let the air flow freely.

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3. Fallen Debris

The obstruction could be items that have fallen into the vents. Take out the covers and shine a flashlight into them to see what’s inside. If you see an object that is within reach, then take it out immediately. You could also wear gloves for safety if you are unsure what you are getting. For hard to reach items, you can try using a long wire or stick.

Furnace Fuel & Ignition Problems

gas furnace flame

A furnace that turns on but doesn’t produce heat may be suffering from low fuel. Without an energy source, it won’t be able to do much for you. If you are dependent on gas, then make sure that the gas valve is open. You can also call the gas company to check whether there is a service interruption. If so, then ask them when things will normalize.

If you are using a tank of propane or heating oil, then see how much remains in the container. Get a refill if necessary. You can prevent this from happening again by regularly keeping tabs on the remaining fuel and being mindful of your consumption rate. There are also devices that help monitor fuel tank levels. Finally, you can outsource the monitoring to the heating oil company so that they can schedule refills in a timely manner.

Once you are certain that you have ample fuel, turn your attention to the ignition system. This is responsible for starting fuel combustion. If it is not working correctly, then the furnace cannot produce heat. For legacy models, see if the pilot light is out. Consult the manual for steps in relighting this. For new models, check the igniter switch of the electronic ignition system. If the metal strip is dirty, then clean it up carefully and test again.

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Furnaces that turn on but do not heat up leave a lot of homeowners confused. We hope that this article sheds some light on the matter. The next time it happens to you, you will know exactly what you can do to remedy the situation. In case the basic troubleshooting steps above did not fix the issue, escalate to the professionals and schedule a service call. Experts have the training, tools, and experience to solve advanced problems. They can provide a fast and accurate diagnosis that leads to reliable solutions.

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McAllister Energy

McAllister Energy offers high-quality HVAC services in Camden County, New Jersey. We hire only the best, professionally certified technicians who conduct superior heating and cooling services. Some of our HVAC services include HVAC maintenance, heating and cooling installations, repairs, ductless systems, energy audits, and much more. All our techs provide accurate HVAC services on time, every time.

Our company guarantees affordable heating and cooling service rates. Our maintenance services can increase your home’s comfort, energy efficiency, and cost-effectiveness. We can also provide you with a highly energy-efficient HVAC replacement system that fits your budget. Your satisfaction is important to us, so all our work comes with a guarantee. Book a service appointment with McAllister Energy today. We provide free, in-home estimates.

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