Furnace Turns On Then Off After A Few Minutes? (Fix It Now!)
The weather outside is frightful, but your furnace fire ain’t feeling so delightful. If your furnace won’t stay lit, trying to deal with winter weather can become a serious problem. Furnaces that don’t stay lit are more than just a pet peeve. This is a major problem that can harm your wellbeing. So, what’s the deal with this issue, anyway?
There are several reasons why your furnace may not stay lit after being turned on. The most common reasons include:
- Bad Pilot Sensors
- Low Airflow/Bad Filters
- A Bad Pressure Switch
- A Faulty Ignition Board
- A Faulty Draft Inducer Motor
If you are worried about your furnace’s ability to function, it’s important to get to the bottom of this as soon as possible. Thankfully, most fixes are fairly easy to diagnose. This guide will give you a good idea of what to expect.
Troubleshooting A Furnace That Turns Off After A Few Minutes
A furnace that seems to be unwilling to stay on is a serious and valid cause for concern. If you’re a DIYer who has a little bit of furnace knowledge, then you might be able to fix it on your own depending on what the issue is. We broke it down by cause so that you can get a better grip of the fix you’ll need.
Bad Pilot Sensors
A bad pilot sensor, also known as a flame sensor, is the most common culprit of a furnace that won’t stay lit. This is a long, silver metal rod that is found right near the burners, often held in place with a metal wall.
- To check it, remove the flame sensor from the housing and take a look at it. Your flame sensor should not have any cracks in the porcelain, and should not be discolored. If you notice cracks or breaks, you need to replace the sensor.
- If it’s dirty, wipe it down with an abrasive brush and put it back in the furnace. Soot can throw off the sensor’s ability to read, which is why this fix works.
- If you hear a clicking noise when you try to turn it on, it could be a pilot light issue too. These tend to go hand in hand for some reason.
Airflow is one of the other major triggers, and this has to do with your furnace filters more than anything else. A clogged, dirty filter will trap hot air inside your vents. This puts your system at a risk of overheating, which triggers your furnace’s safety features. To prevent a fire, the furnace will shut off.
The easiest way to fix this is to switch out your air filters. In most cases, this will be enough to fix the issue. If that doesn’t work, take a look at your outside ventilation. If there are leaves, nests, or other things blocking it, this could cause it too. When poor ventilation builds up, you might notice that your furnace only blows warm air instead of hot.
A Bad Pressure Switch
Your pressure switch is located in the furnace and reads whether or not the airflow is working. If it detects that there’s a problem with the ventilation, it’ll shut off, which in turn, signals that it’s not safe to continue sending fuel to the furnace light. If your pressure switch is bad, your furnace will shut off within a matter of minutes since the switch won’t close.
You can usually test if the switch is working by using a multimeter. If you do not see any feedback, then you need to replace the pressure switch.
A Bad Draft Inducer Motor
This is a common issue that tends to be comorbid with a bad pressure switch. The draft inducer motor looks like a “turbo engine” that can be found inside the furnace. As the name suggests, this motor is what feeds ventilation into your furnace, giving it enough air to heat your home appropriately.
If your pressure switch failed, chances are that you might have a bad draft inducer motor too. It’s what brings air into the ignitor, which is what keeps your flame going. Before you assume the motor is bad, replace the switch and check to see fi your motor has any clogs near the opening of the motor. Sometimes, dust or other materials can get in the way, reducing its efficacy.
A Faulty Ignition Board
With a direct ignition furnace, your furnace’s pilot light, gas feed, and light strength are all controlled by a computerized ignition board. Sadly, this is one fix that you will not be able to diagnose fairly easily. Though a multimeter can help, you may need to call a professional repairman for this.
An ignition board that has gone bad cannot be fixed by typical means. You will need to replace it.
Bad Gas Pressure
In order for your furnace to stay lit, it needs to have a certain level of gas pressure to work its magic. Check the pressure of your gas valve using a manometer. If the pressure reading you get doesn’t match what your pressure should be for your model (check your owner’s manual here!) then you have a pressure problem.
You might be able to increase the pressure by tweaking the gas pressure valve. However, this is usually something that you’re better off calling an HVAC tech for.
Remember when we mentioned that most furnaces have a function that prevents them from overheating? Though it’s exceedingly rare, there are moments where parts that have little to do with the pilot could have gone bad and caused conditions that make your furnace prone to overheating.
In this situation, you actually have a furnace that’s working perfectly—at least, for the safeguards. If you have reason to believe your furnace is overheating (such as it being hot to the touch), cease usage immediately and call an HVAC tech.
When Should You Call A Professional?
When it comes to a furnace that flits between being on and off, it’s best to give a DIY shot to minor fixes like getting better ventilation or fixing your pilot sensor. These are easy fixes to do and are fairly foolproof. Many experienced DIYers might also be able to do well with gas pressure issues as well.
However, when it comes to issues involving pressure switches, draft inducer motors, ignition motors, or a risk of repeated overheating, then you should call a professional. These fixes tend to be far more complex and professional intervention may actually be required by law depending on your local building codes.
How Much Does Furnace Repair Cost?
The dollar amount you should expect to pay to repair your furnace all hinges on what is wrong with the furnace. If you have a furnace pilot sensor that needs replacement, you should expect it to cost at least $25 to $50 for parts alone, if you are doing a DIY repair. A set of furnace filters can cost between $25 to $105, depending on how many you need.
The price of more complicated fixes, particularly those that require an HVAC professional, can get even pricier. A typical furnace repair will clock in around $282 on average, with a normal range being between $131 to $469. Since this is a fairly commonplace issue, you should expect your price tag to be closer to the $131 range.
Is This Problem A Dangerous One?
Honestly, it can be. If your furnace is starting to act up as a result of overheating or a gas leak, then it needs to be addressed immediately. Otherwise, you run the risk of having an explosion, carbon monoxide poisoning, or other serious side effects. If we’re going on a more conservative stance, any issue with a furnace should be treated as a serious danger.
Should you repair or replace your furnace?
The easiest way to make the right call for your furnace hinges on the furnace’s age. If your furnace is less than 10 years of age, or if the furnace is still under warranty, you should repair your furnace. Furnaces that are 15 years or older are better off replaced, simply because they will often start breaking down more and more frequently.Another way to measure out the benefits is through cost. If the repair costs less than a third of the price of replacement, it’s usually better to fix it. If the fix is more than half the price, it’s better to replace the furnace regardless of what age it happens to be.
How long should a furnace last?
With proper maintenance, you should be able to make a furnace last at least 15 years, if not 20 or more. However, that doesn’t mean that you should always try to make it last. If you notice that your furnace is having more problems than you care to fix, check to see if it’s still in warranty.A furnace under warranty will make it easier for you to call up the company and ask for repairs. If you notice serious problems immediately after the warranty is gone, it may be time to get a new model.
Ossiana Tepfenhart is an expert writer, focusing on interior design and general home tips. Writing is her life, and it's what she does best. Her interests include art and real estate investments.
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