Why won’t my furnace’s pilot light stay lit?
The most common reason the furnace pilot light won’t stay lit. A furnace thermocouple is a safety feature that regulates gas flow to your system based on whether the pilot light is on.
What causes a gas furnace flame sensor to go bad?
Possible causes: Bad flame sensor. The flame sensor tells your furnace that the gas is lit. Poor flame sensor positioning. The flame sensor might be fine, but isn’t positioned right and so cannot sense the pilot’s flame. Defective ignition board.
Why does my furnace keep going on and off?
Situation: You turn the thermostat up, the furnace ignites and the burner comes on. The furnace stays on for a while (maybe 1 minute, maybe 10 minutes) and then goes out. The fan continues to run even though the flames and pilot light go out. Overheating. Your furnace has a limit switch that keeps it from running if the heat exchanger is too hot.
How does a gas furnace ignitor light up?
Upon detecting the presence of gas, the pilot ignitor lights via an electric spark or hot surface ignition. Upon sensing the flame on the pilot, a flame sensor signals your furnace that there’s a flame to burn.
How do you fix a furnace that won't stay lit?
0:245:33Furnace Won't Stay Lit - YouTubeYouTubeStart of suggested clipEnd of suggested clipAnd easiest test is to take it out and clean any deposits off of it with some fine sandpaper. Let meMoreAnd easiest test is to take it out and clean any deposits off of it with some fine sandpaper. Let me see if I could get a little closer for you.
Why does my furnace turn off after a few minutes?
If your furnace shuts down after a few minutes, it's likely due to a faulty or unhygienic flame sensor. This crucial component intends to monitor the gas burner. Also, when a flame sensor cannot detect the burner, the furnace runs for a few moments before shutting down and restarting.
Why does my furnace keep shutting off after a few seconds?
A common reason a furnace short cycles is because the heat exchanger, the part that heats your air, is getting too hot due to a lack of airflow. Once the heat exchanger overheats, it trips the high limit switch, which shuts the furnace down to protect it.
What causes furnace to lose flame?
The most common causes for a furnace flame going out include: A dirty or malfunctioning sensor. Defective ignition board. Insufficient gas pressure.
How do I clean my furnace flame sensor?
1:053:46Furnace Cycling On and Off - Flame Sensor Cleaning - YouTubeYouTubeStart of suggested clipEnd of suggested clipSo if you have a situation like this what you have 90% of the time is just a dirty flame sensor. SoMoreSo if you have a situation like this what you have 90% of the time is just a dirty flame sensor. So we'll go through the steps on how to clean it. So the right side of the furnace.
Why does my furnace start then stop and start again?
This behavior is caused by something cutting short each furnace cycle since your furnace is being forced into a short cycle to keep your home the temperature set on your thermostat. A furnace that is sized properly for your home should start and stop 3-8 times in an hour.
How do I know if my furnace is short cycling?
If your furnace turns on and off repeatedly for short bursts of time, not allowing the house to reach its proper temperature, it is short-cycling.
Why does my furnace turn off then right back on?
Your furnace may be shutting down because the heat exchanger is overheating. When the heat exchanger overheats, the furnace shuts down to protect it from cracking. When the exchanger cools, the furnace cycles back on. After overheating several times, it's only a matter of time before the heat exchanger cracks.
How do I know if my furnace flame sensor is bad?
Signs of a bad flame sensor Furnace burners turn on but go out after a few seconds. Soot and other debris is covering the end of the sensor (cleaning the flame sensor may fix this issue rather than a flame sensor replacement) Tip of flame sensor is black. Porcelain/sensor casing is cracked.
What are the symptoms of a dirty flame sensor?
6 Signs of a Malfunctioning Gas Furnace Flame SensorYellow Burner Flames. Open up or glance through the peephole of your gas furnace to see the color of the flames firing up in the burner. ... Rusted Flue Lines. ... High Utility Bills. ... Water Leaks. ... Old Age. ... Constant Thermostat Adjustments.
Why does my furnace stop every 5 minutes?
If your furnace turns off after a few minutes, there is a good chance it is caused by a faulty or dirty flame sensor. This vital component is designed to keep an eye on the gas burner. When it cannot sense that burner, the furnace runs then shuts off and starts again. This could be a relatively easy fix.
How do I know if my furnace is short cycling?
If your furnace turns on and off repeatedly for short bursts of time, not allowing the house to reach its proper temperature, it is short-cycling.
How long should furnace run before shutting off?
With all that being said, if there are no extreme factors involved, the average run time for a furnace is 10-15 minutes per cycle. Your furnace may need to run two to three times an hour to maintain your desired temperature if your home has average insulation.
How often should my furnace turn on and off?
3-8 times per hourOn average, furnaces should kick on and off anywhere from 3-8 times per hour. However, if your furnace does so more frequently, don't assume it's short cycling just yet.
Why won't my furnace stay lit?
A furnace that doesn’t stay lit can be caused by an overheating exchanger. That also means there’s limited air flow getting into the heat exchanger, which can be caused by these 3 issues:
Why does my furnace turn on and off?
If your furnace turns on several times and each time it goes off after a few seconds, you probably have a dirty flame sensor rod.
What to do if your thermostat is not working?
So, call an expert HVAC technician to check if your thermostat has issues and if it’s the one causing the furnace not to stay lit. The HVAC pro will advise if you need to replace the thermostat or a simple fixing or adjusting is required.
What is a furnace thermocouple?
A furnace thermocouple is a sensor that detects the functioning of the pilot light. If the pilot light goes off, the thermocouple shuts off the gas valve to preempt any accidents.
What happens if a furnace doesn't shut down?
The worst-case scenario is that the safety features could also be faulty, and if the overheating furnace doesn’t shut down, that could start a fire.
How long does a furnace last?
Furnaces are created to work in cycles that last 10-15 minutes under normal circumstances. Sometimes, however, your furnace runs for a few minutes then stops.
How old should a furnace be to replace it?
There’s no negotiating with an old dysfunctional furnace. You simply need to replace it. The U.S. Department of Energy advises that a furnace that’s 20 years or older should be replaced even if it works fine .
Broken thermocouple
A thermocouple is a safety component that uses two different types of metal wire to measure the temperature of the flame. This is so it can manage the gas flow to the burner. When the thermocouple senses that the flame isn’t hot enough, it shuts off the flow of gas so that your home isn’t filled with flammable gas.
Tripping pressure switch
A pressure switch is another safety device, mostly on newer systems, that will shut your system down if it detects the venting in your system isn’t operating correctly. Improper venting can be caused by dirty air filters, blockages or obstructions in the ductwork, or blocked registers.
Why won't my pilot light stay lit?
However, if your thermocouple is damaged, dirty, or bent, it may inaccurately sense that your pilot light is off and turn off the flow of gas to your system . Without any gas supply , your pilot light won’t stay lit.
How to keep a furnace pilot light lit?
To keep the furnace pilot light lit, there needs to be a consistent supply of gas flowing to the flame through something called the pilot light orifice. If this tube is clogged or dirty, there won’t be enough gas flow to keep the flame strong. If the flame isn’t strong enough, the thermocouple won’t sense it and may shut off the supply ...
What happens if the pilot light is not strong enough?
If the flame isn’t strong enough, the thermocouple won’t sense it and may shut off the supply of gas to the flame. You may issue the pilot light orifice if you notice that your pilot light flame is a weak yellow color rather than blue.
What is a bad thermocouple?
Bad Thermocouple. A furnace thermocouple is a safety feature that regulates gas flow to your system based on whether the pilot light is on. In simple terms, the thermocouple checks to see if your pilot light flame is lit and turns off the gas flow if it senses that your pilot light is off, so you don’t have gas building up in your home.
What does it mean when a pilot light goes out?
If your gas valve is set to OFF or is faulty in some way, a consistent supply of gas won’t be delivered to your pilot light, resulting in a flame that goes out.
What does a gas regulator do?
A gas regulator decreases gas pressure before it makes its way into your home and to your appliances. As your gas regulator ages, it can struggle to supply your home with a strong, consistent supply of gas, which can result in a gas pressure that’s not strong enough to keep your furnace’s flame lit.
Why Won’t Gas Heater Pilot Light Stay Lit?
Or maybe it stays on a little longer but not long enough to light the furnace burners.
What sends more gas to the furnace burners?
The gas valve sends even more gas to the furnace burners.
Why does my pilot flame go out?
Another reason the pilot flame may go out without lighting the main burner is the incorrect flame sensor positioning. The flame sensor must be close enough to the pilot flame to detect the flame.
What happens when a flame sensor is activated?
As we’ve seen, once the flame sensor signals the presence of a flame, the gas valve springs into action to provide sufficient gas for the heating process. However, imagine in an instance where the gas valve is compromised!
How to tell if a gas burner is blocked?
The first thing you want to check is whether the burners get gas in the first place. If they don’t, then the most likely issue is a clogged or blocked burner. A common sign of blocked burners is an unhealthy flame that’s yellow with lots of smoke. Clogged burners may also have an irregular, weak flame.
Why does my flame sensor lose its capacity?
Flame sensors can lose flame sensing capacity for several reasons. For instance, a flame sensor may be become worn naturally. It may also become damaged.
Why do furnaces skip step 4?
Furnaces with standing pilot lights are also slightly different. They skip step #4 because the pilot light remains lit throughout.
Why is my gas furnace not turning off?
Gas Valve Problems. Your gas furnace has a gas valve that could affect the pilot light since it supplies the flame with gas. Check the gas valve to make sure it's not set to "off.". If it's on and there's still an issue, the gas valve could be faulty.
What happens when the pilot light is out on a furnace?
If the pilot light is out, there's no way for it to light the main burner, which means your house will get cold quickly.
Why is my pilot light not working?
The thermocouple is often the culprit if your pilot light doesn't stay lit. If the thermocouple gets dirty, it could block the sensor. You can clean your thermocouple using an emery cloth or steel wool on the sensor tip to get rid of corrosion. If it's clean but the pilot light continues going out, the thermocouple could be damaged or bent.
Where is the pilot light on a furnace?
The pilot light location can vary, but it's usually near the bottom of the furnace, often behind an access panel. Look for a gas valve and two copper tubes attached to the control valve to lead you to the pilot light. Refer to the owner's manual if you still have it or look for a label on the furnace with instructions on how to light it ...
How does a standing pilot light work?
How Standing Pilot Lights Work. Newer furnaces use electronic or hot-surface ignitors, but an older furnace might have a standing pilot light, which is a flame that burns continuously. The furnace supplies a constant, small amount of gas to the pilot light to keep it burning. It serves as the ignition source for the main burner.
Why does my stove burner shut off after 6 seconds?
If the flame sensor is clean but the burners still shut off around 6 seconds after ignition, this may be the result of a faulty ignition control.
How does a gas furnace protect against over temperature?
Gas furnaces are protected against over-temperature by a high-limit switch. When the high-limit switch trips it will turn-off the burners. When the heat chamber cools, the limit switch will re-activate and allow the burners to re-fire.
Why does my switch trip?
Possible causes are a bad blower motor, a clogged air filter, blocked or restricted registers, or under-sized ductwork. A high-limit switch trip caused by no airflow (bad blower) will typically occur within 30-60 seconds after ignition. A high-limit switch trip caused by low airflow may only occur after long run cycles.
Why do gas furnaces use pressure switches?
Most newer gas furnaces use one or more pressure switches to monitor for proper venting and condensate drainage. It is not unusual for a partially restricted venting system or a clogged drain to allow a furnace to fire and then shut-off some time during a heating cycle.
How long does it take for a furnace to start after opening the gas valve?
This is accomplished by a flame sensor. If the flame sensor does not detect a flame within 6 seconds after opening the gas valve, the ignition cycle is terminated.
Why does my heat pump trip?
High limit trips are generally caused by a lack of airflow across the heat chamber. Possible causes are a bad blower motor, a clogged air filter, blocked or restricted registers, or under-sized ductwork.
What causes a high limit switch trip?
A high-limit switch trip caused by low airflow may only occur after long run cycles.
