A gas furnace that turns off after a few minutes won’t heat the house properly, leaving you freezing in the cold, and you don’t want that. So, it’s time to know the possible causes of this issue and also involve a furnace repair service.

How Long Is A Regular Gas Furnace Heating Cycle?

Before understanding the causes of your furnace turning off suddenly just a few minutes after starting (short cycling), you should know what’s normal for furnaces and what’s not.

A regular gas furnace’s heating cycle lasts for 10-20 minutes. This happens about 2-4 times every hour. But if your furnace turns off just after a few minutes, such as 5 minutes, then it’s short cycling and it’s a problem.

Causes Of A Gas Furnace Turning Off After A Few Minutes

Clogged Or Dirty Air Filter

A clogged air filter is a common cause of most gas furnace problems. There is an air filter near the end of the return vent to keep dust and other contaminants from entering the system. It protects the furnace and all of its components, and also allows sufficient airflow.

When the air filter is clogged due to skipping maintenance, the furnace won’t receive enough air to heat. This means poor airflow. It leads to insufficient heating, an overheating furnace, and the unit either running for too long or turning off too quickly.

Your gas furnace maintenance schedule should include cleaning the furnace filter once every 1-2 months. But you should inspect the filter every month and clean it if it appears too clogged.

Faulty Thermostat Or Other Thermostat Problems

If the thermostat is faulty and not detecting your home’s temperature correctly, it can cause the furnace to turn off too quickly. Many types of thermostat issues lead to short cycling.

Improper Thermostat Placement: If the thermostat is installed near a heat source, it will “feel” warm sooner than the room, so it will signal the furnace to stop heating.

Low Battery: When a thermostat’s battery is low, it can go haywire. This can affect the proper functioning of the thermostat. It may signal the furnace to turn off when not required.

Faulty Thermostat: A bad thermostat that has stopped functioning properly will send erratic signals to the furnace, causing it to run for too long or short cycle.

Dirty Thermostat: Dust can build up on the thermostat, which can hinder its ability to detect temperature changes accurately.

Blocked Furnace Exhaust Flue

A furnace exhaust flue is the pipe that carries the smoke and gases out of the furnace and releases them outside. An exhaust flue is to a furnace what a chimney is to a fireplace.

Due to leaves, debris, snow, or other things, these pipes can be blocked. So, the toxic gases have nowhere to go. This causes furnace efficiency problems, overheating, carbon monoxide release in the indoor air, and the furnace shutting down too frequently.

So, check the furnace exhaust vent, which is usually a white or black PVC pipe and will be visible on the exterior of your house. Clean it and also inspect the entire furnace vent system for blockages and damage.

Closed Or Blocked Air Vents

There are two types of air vents: supply vents (supply heated air to the house) and return vents (supply air to the furnace for heating). If these vents are closed or blocked by anything, the airflow will be affected. There will be issues like insufficient and inconsistent heating, unusual odors and strange noises, and the furnace short-cycling.

Supply Air Vents

Firstly, check the supply air vents. You can close a few, but closing many will reduce the airflow, leading to many problems, including the furnace either short-cycling or running for too long. Both of these problems can cause overheating. If you haven’t closed a vent, check for furniture items or curtains blocking the air vents.

Return Air Vents

Similarly, dirty or blocked return air vents are not good for your furnace as well. This directly impacts the airflow and the heating capability of the furnace and because of this, the furnace may keep turning off. Commonly, something obstructing the return air vents, dust and debris buildup on the vents, and a clogged furnace filter can create this problem. So, clean the vents and the furnace filter. Other issues can be related to the ductwork design and installation, so consult HVAC companies Port Jefferson for an inspection.

Dirty Or Faulty Flame Sensor

A furnace flame sensor is a safety device for protecting you from gas leaks and explosion hazards. It detects flame in the ignition chamber and when there is no flame, it shuts off the gas supply. So, if the flame sensor is dirty or faulty, it won’t perform its job correctly and due to this, the furnace will turn on, only to be turned off within a few minutes.

So, inspect the flame sensor so you can see if it’s just dirty or malfunctioning. A dirty flame sensor can be cleaned and damaged wiring can be repaired, but a corroded or damaged flame sensor should be replaced.

Low Gas Pressure

Low or intermittent gas pressure will make the furnace turn on and off unexpectedly, leading to many problems, including short cycling. Check the gas supply and make sure the valve is open, the valve is not faulty, and there are no leaks in the gas pipes.

Overheating

Overheating triggers the limit switch to turn off the furnace. A limit switch is a safety device that is for the sole purpose of switching off the furnace to keep it from overheating and catching fire.

A furnace can overheat due to many reasons. Some of them are also explained here, or the overheating problem can be due to things like an old furnace, a damaged or dirty heat exchanger, clogged burners, and others.

Bad Limit Switch

A limit switch or high limit switch turns off the furnace, when required, to keep it from overheating. If the limit switch is bad, it will not work properly and because of this, the furnace may overheat and other safety devices trigger the furnace to shut down. So, the furnace may turn off prematurely without finishing its cycle and won’t warm the house as required.

Many times, a bad limit switch means there is another issue, like a clogged air filter or poor airflow, so inspecting the furnace is important.

Malfunctioning Blower Motor

The blower fan motor allows the blower to run, which allows air into your house and it keeps the heat exchanger from becoming too hot. A bad blower motor will stop the airflow, so the furnace will overheat, leading to an immediate switch off for safety.

Age and wear and tear can be common causes of a bad blower motor. Other issues can be clogged air filters, lack of maintenance, blocked vents, faulty blower capacitor, furnace overheating due to another reason, electrical issues, etc. Hire a professional to inspect the blower motor and other parts of your furnace.

Conclusion

A furnace turning off after a few minutes can be a sign of various problems, like a clogged air filter, a faulty thermostat, a blocked furnace exhaust flue, blocked air vents, a faulty flame sensor, a bad limit switch, and others. So, call in furnace services Huntington that can inspect your furnace and fix it.