Furnace Troubleshooting – Oil Furnace Starts Then Stops – (2021) Owner’s Guide

| Last Updated: June 10, 2021

Are you unable to enjoy a warm, pleasant, and cozy environment because of furnace problems? 

Does your furnace run for a few minutes and then shut off, making it difficult for you to relax at home? 

There can be many reasons for this problem. Here we will discuss a few likely causes that are responsible for shutting off your furnace after every few minutes and their remedies so that you can make your home a comfortable place for you and your family.

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What Is It Called When a Furnace Starts and Stops?

A furnace that starts and then stops in a few minutes is a common problem known as short cycling. You start up your furnace, and it begins to heat up your home, but only after running for a short time, it shuts off quickly. This kind of fast heating cycle is not normal and can damage your furnace. It also indicates that your furnace requires some repairs to correct the underlying cause of short cycling. 

A furnace that is proportionate to your home size should typically run three to eight heating cycles per hour, depending on your preference and the characteristics of your home. In case your furnace experiences more cycles, then it may be short cycling. It is also possible that high temperatures are causing more frequent cycles, or the furnace requires additional insulation or is undersized.   

What Causes a Furnace to Start and Stop?

There are a few reasons that can cause short cycling. These include:

Furnace Overheating 

The safety devices in your furnace may trip due to overheating, which may shut down the heating cycle to prevent danger and damage. High temperatures are a common cause of short cycling. If the temperature of the furnace gets too high, the high-limit switch will automatically shut off the furnace. 

Restricted Airflow

Restricted airflow is one of the common causes of short cycling. When an air filter is not installed correctly, is dirty, or is too restrictive, it can result in limited airflow through the system. Airflow can also become restricted in case there are any broken or blocked room vents. Moreover, evaporator coils caked with debris can result in airflow restrictions. 

Thermostat Issues

Incorrect placement of thermostat, for example, in areas that experience frequent temperature fluctuations can also cause short cycling. These areas may include exterior walls, near heat sources, or near doors and windows. 

Flame Rod Failure 

The furnace will also shut down when the flame rod of the furnace is unable to sense the burner flame.   

DIY Steps to Fix an Oil Furnace that Starts then Stops 

In some instances, fixing an oil furnace that starts and stops is very simple and can be done in a few steps:

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Defective Pressure Switch

Sufficient airflow through the furnace causes the pressure switch to close. However, even with the proper airflow, the pressure switch might not close if it is not working, thus causing the ignition to stall.

In this case, the furnace will shut off. Use a multimeter to test if the pressure switch is defective. Simply replace the pressure switch if it does not have continuity. 

Dirty Flame Sensor

The purpose of a flame sensor is to detect the presence of the flame. In case the flame sensor doesn’t detect a flame, the control board may shut off voltage to stop the furnace from heating. A dirty flame sensor may also fail to detect a flame. Use a good-quality abrasive pad to clean the flame sensor. Replace the flame sensor if the furnace still doesn’t heat.  

Airflow Problem

Proper airflow is vital for the furnace to keep burning. The furnace draws air from its surrounding area. If it is located in a cramped storage room or in a utility closet, there may not be sufficient air to provide proper heat. Also, make sure that there are no obstructions at the air inlet if your furnace pulls in air from outside the home.  

Defective Control Board

The control board supplies power to your furnace. If this is broken or defective, it can cause your furnace to start and shut off rather quickly. Unfortunately, it is not possible to fix a faulty control board. You will simply have to replace it so that your furnace could run properly. 

Safety Considerations For Fixing an Oil Furnace

Regular maintenance not only keeps your furnace in good shape but it also ensures that there are no accidents. However, it is vital to take some safety precautions when you are fixing your oil furnace. Some tips for this include:

Keep Flammable Items Away

Keep the items that may catch fire away from heat. In some homes, the furnace room is also used as a laundry or for storage. If your furnace room has multiple purposes, then the best practice is to keep it as organized as possible. Avoid hanging clothes near or from furnace equipment if the room is used as a laundry room as well. 

Any item left close to the furnace could become a hazard. Use airtight containers to store cleaning solutions as ammonia fumes could damage the furnace’s heat exchanger. Also, make sure to keep wood scraps, gasoline, papers, paint or paint thinners, old rags, and sawdust away from the furnace.

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Vacuum

Dust and lint are a hazard around your furnace. By vacuuming regularly inside and around your furnace, you can avoid dust build-up and prevent it from becoming a fire hazard.  

Keep Air Flowing

Fresh air is vital for a furnace to efficiently and evenly heat your home. If it does not get sufficient air, it may use up the oxygen in your home, which can be quite dangerous for you and your family. 

Moreover, any blockage to airflow can hinder the performance of your furnace, causing it to work harder and costing you more money. It is best to clear obstructions and open floor registers to ensure even heating throughout your home.  

When Is It Time to Call in a Professional?

The season to fire up that furnace is upon us. But before you make a cup of hot chocolate and grab your blanket, you have to get your furnace ready for winter. After sitting idle during the long months of summer, your furnace will require some maintenance before you can start using it again. 

If you encounter a problem with your furnace, the first thing that you should do is consult the manufacturer’s website or the instruction booklet provided. However, if it is not a simple fix and you are unsure of the underlying cause, then it is best to call in a professional.  

Conclusion

If your furnace starts and then stops after a few minutes, then it could be a small issue or the sign of a much bigger problem. People who often undertake DIY projects might be able to solve the problem with their furnace in an afternoon, while some people may need professional help. 

Making major modifications to your furnace if you are unsure can be quite dangerous for you and your family. Be sure to engage the services of a professional to ensure that your furnace is in excellent shape to handle the coming winter months.




My name is Bob Wells and I am a retired HVAC tech from Washington state. I am currently retired and no longer do much with HVAC, however, I feel like I have a lot of knowledge in the subject and I wanted to create a website where I could talk about what I've learned and help upcoming HVAC techs. Find more info about me and HVAC Training 101.