Remove the screw(s) and disconnect wire, Once removed you can clean the sensor with a scotch brite pad, if you do not have one then just use a clean rag for now. If you’ve eliminated a dirty air filter as the cause, the next most likely culprit for … Fill in your details below or click an icon to log in: You are commenting using your WordPress.com account. You can also unplug the furnace as well. If you cleaned your flame sensor but it’s still malfunctioning, you may need to replace it. One of those components is the flame sensor. If the flame sensor does not detect a flame, as a safety precaution, the control board will shut off power to the gas valve to prevent the furnace from heating. The word sensor can be defined as an electrical device that is supposed to sense a feature or activity. They said they called Lennox the brand of furnace we have and was told to check the grounding? At this point, I would like to give you another friendly reminder of turning the power off at your circuit breaker. There’s not much to this component – you’ll see a thin, rounded rod about the diameter of a coat hanger near your row of burners. Once you have the proper tools, you can start the cleaning process. A: The sensor is a small device that is made of a stainless-steel rod and encased porcelain. You may also find the white porcelain of the flame sensor cracked or broken. Lennox gas furnaces contain an important safety component known as a flame sensor. I always recommend you do this when repairing, installing or maintaining your home appliances. As long as the component senses the flame, it sends a message to the main furnace control board telling it to keep the main burner on and the gas valve open. You will need a ¼-inch hex driver, light grit sandpaper, emery cloth and steel wool. This toggle switch should be mounted on or somewhere near the furnace. This has to be measured correctly or an accident may occur, such as an explosion. You should be getting a low resistance reading on your multimeter. The first step is to shut off all the power going to the furnace. Very good- Take care. Gas Furnace Flame Sensor Troubleshooting and Repair Video Is your gas furnace short cycling on and off? advice on heating and air cooling repairs from an HVAC-R professional, . One symptom of a bad flame sensors is the ignition, which has already been discussed. It appears the blinking flame LED means the current is marginal. How the flame sensor works is by a small AC electrical charge going through the sensor and it uses the flame to carry the electrical power to ground. If this is the case, you will need to shut off the gas going to the furnace. The first reason can be a dirty flame sensor. The best way to ensure that this device is working properly, and to prevent flame … In fact, many techs will just change the sensor for a new one as part of their maintenance procedures. If flame sensor requires cleaning more often then once a year it should be replaced, or check for other problems like vent stack temperature, gas pressure, or primary air need to be adjusted. • Normal furnace operation. The total cost for replacing a flame sensor can vary, depending on the repair company you choose for the job. Thermostat Issues. Examine the settings on the thermostat. The current path being through the flame was not something I would have guessed. See some steps that might help you fix your home furnace. ( Log Out / I am an electrical engineer- so I understand the concept well. Another sign is soot that covers the tip of the sensor. I was not aware of exactly how the flame sensor worked. After cleaning is complete, replace the flame sensor. Therefore, any type of dust could affect its performance. The way it works is simple. Thanks for your comment, I try to make things easier for everyone to help them determine what is wrong and to make repairs. The flame sensor has a coating on it to make it last a long time and will get worn off by over cleaning, so it is best to only clean rod when it is needed. This can include the cost of travel and the diagnostics charge. A: This can be due to a few factors. The rest of my comment is exactly everything Tony said. Think of it as a chain reaction. The blue flame indicates that your gas furnace is burning the fuel safely and efficiently. Remove the flame sensor. I said change the flame sensor, they haven’t yet. Your gas furnace flame sensor is just one part a built in safety system for your furnace. Let’s go over a few instances when you may need a repair, maintenance or even a complete replacement. To avoid danger, it is very important to shut off the power to your furnace (or any other appliance), … If it is cracked, you could be dealing with a broken flame sensor. If the pilot flame is not focused on the flame sensor of the flame rod assembly then you might need to clean the orifice in the pilot assembly or try to adjust the pilot up more if the gas valve has an option to adjust the pilot up more so it burns higher. I cleaned the flame sensor and it’s working as it should. Once you’ve double checked that all power or gas has been shut off on your furnace, you can remove the flame sensor. The problem was exactly as outlined and so was the solution. The flame sensor checks to see if a flame is present. First of all, if the oil burner goes on and off too much, clean or … Nice well written and well explained article. As an Amazon Associate we earn from qualifying purchases. Look at the filter. Shut power off to the furnace while you are working, you will find a light switch high on wall or in the ceiling. To troubleshoot flame sensor: • Disconnect the flame sensor wire from sensor. All you need is a multimeter and a light. This should complete the process of cleaning the sensor. Click here to see my post “first check thermostat” You're trying to remove oxides that build up over time. A: The flame sensor can be easy to clean if you follow the steps carefully. The Furnace Won’t Stay On If the furnace fires up but then shuts off after a few minutes, it could be that the control board is faulty. However, if you always keep your flame sensor clean, it could just be that the sensor has gone bad. If you’re willing to risk $120 and buy all three parts ahead of time, you may be able to fix your own furnace in less than an hour and save a $125 service call. The price ranges can be anywhere from $350 to as much as $500. You can keep your sensor clean by maintaining it on a regular basis. You may also find the white porcelain of the flame sensor cracked or broken. The flame rod appears to be crumbling and is jagged at the tip. This central controller operates the gas or fuel valves for releasing the combustible materials into the burning chamber of the furnace or boiler. The furnace comes with many components to analyze. Furnace Not Working—Oil Burner. The whole process is an ignition sequence. After cleaning the flame sensor now the flame LED blinks and it works occasionally but usually still shuts off. Next, you’ll need to loosen the clamp that secures the sensor in place. I appreciate you for posting when you’ve got the opportunity, Guess I will just bookmark this All you need to do now is disconnect the leads, which can be done by pulling the wire boots. And they don’t know why. I tried wiggling all the ground wires to no avail. • Flame sensor Is coated/oxidized. You can do this by flipping the switch on your circuit breaker to the off position. I can simplify this a bit for you. A: Now we’re getting to the good stuff. Remove access covers as needed: on a gas fired water heater you will need to remove the manifold door at the heater bottom in order to access the end of the thermocouple that mounts on and monitors the pilot flame. You may also notice a sensor filled with corrosion and soot. This would include the flame sensor. You are spot on. burners ignite (light up) the flame sensor picks up the heat from the furnace's main burning and says, "YES," and sends a signal back to the main furnace control board saying that it is OK to let the main burner stay on. If you furnace begins clicking and the blower turns on and off again, this may indicate a faulty flame sensor. The flame sensor sends an electrical signal to a central controller. In the picture you will see a 1/8 inch round rod in the flame, that is the flame sensor. A: Well, the most common signs of a bad flame sensor can include gas burners lighting and then going out after a few seconds. Although the word flame goes hand in hand with furnace, the word sensor may throw you off a bit. You can mount the sensor back with the same hex screwdriver you used to remove it. Next, simply replace the flame sensor back in its place. The same thing goes for a furnace. In many cases, if the furnace startup sequence gets as far as ignition then immediately shuts back off, it can generally be traced to the Flame Sensor. Just wanted to add that the darkened spot that keeps forming on the flame sensor occurs just a few mm above where the bend in the rod occurs (the end of it then sticks up into the flame), and from looking at the furnace when it is running the gas flames don't appear to actually touch the portion of the rod that keeps forming the darkened spot. Thank you very much. I’ve had my heater quit on me in the middle of winter, and it was not fun. As a safety precaution, you can replace and install a new flame sensor every two to three years. As the gas valve solenoid could be faulty or there could be low gas pressure. Change ), You are commenting using your Twitter account. As with any mechanical part, you should always keep it clean for optimal performance. The first thing you should check that you have is the necessary equipment. Q: What does a flame sensor do in a furnace? If the flame sensor does not detect a flame, the co...ntrol board will shut off voltage to the gas valve to prevent the furnace from heating. The inline gas valve should be opened. Also check flame quality, sharp blue flame and not lifting off burner. This is why the clicking sound continues. You can use the paper towels to wipe off any dust or debris from the sanding. I’ll start the hunt for a replacement. As far as flame sensor testing a qualified tech can check with a meter DC micro amps output and see if flame sense is sending signal to the board for approval to keep gas valve open. The good thing about this step is that it’s easy to do. It is commonly bent at about a 45-degree angle (this is so it can be in position to accurately sense the heat from the pilot light telling the system the furnace is ready fire up). The flame sensor is an essential part of the furnace’s safety system. The flame sensor’s job is to create a current of electricity. I actually ordered a new flame sensor yesterday but after reading your post it doesn’t sound like it should really go bad if the ceramic isn’t damaged. Hi, great post. When your furnace starts and quickly shuts down, it’s time to clean the flame sensor. A furnace thermocouple is a device on a standing pilot gas furnace that’s responsible for opening and closing the main gas line to your home’s heating system.. A slim, rod-shaped flame sensor sits in the path of your pilot flame where it collects and then transfers heat down via a flexible connector (wire or tube) to signal, through an electrical charge, that the main gas valve should open. Furnace Blowing Cold Air. Keep any mounting screws for re-use. Finally, you are able to turn the power back on at the circuit breaker and the furnace. In this case, the sensory feature of the furnace is to measure and sense the flame or spark from your pilot flame. The flame sensor has a coating on it to make it last a long time and will get worn off by over cleaning, so it is best to only clean rod when it is needed. I have a Magic Chef G6A75D-11 that is exhibiting symptoms indicative of a faulty flame sensor (blowing intermittently, not responsive to thermostat temp changes). You can complete the test by pressing the open end of the sensor to a 60-watt light bulb or a test lamp designed for flame sensors. A flame sensor measures current through the flame, so series current must be read. Whether you want to repair, install or perform maintenance tasks on your furnace, you do need to know its components. Some times the burner and any grounding surface will get dirty and need to be cleaned as well. Change ), You are commenting using your Facebook account. Mike, Flame sensors have a coating on them that will get worn off after it is cleaned or by age. After 3 to 5 tries the control board will lock the furnace out for 3 hours, which can be reset by cycling power or thermostat. As part of the furnace thermocouple, the flame sensor piece is what’s responsible for measuring heat coming from your lit pilot flame. Some people like to clean every year but I advice not to, It is best to clean only when needed since the protective coating will be removed with over cleaning. I am having trouble finding a replacement. You will have to find the flame sensor to perform the test. Enter your email address to follow this blog and receive notifications of new posts by email. Once the rod is cleaned reconnect the wire and screws making sure the rod sits in the flame. As with any major appliance, safety features are always important. Thanks. In this case, you can try to replace the flame sensor yourself. As always, turn off all electrical power to the furnace while you are performing this repair. Try cleaning the flame sensor with a fine abrasive pad. You may find many reasons why a flame sensor is not working. Make sure that you also look at the porcelain on the sensor. I think I will have the havc tech read this because he, and other techs have cleaned the flame sensor at least 3 times this year, and it keeps getting dirty they tell me. If still problems try temporary ground. If a wire is attached to the sensor, you may have to detach it to give yourself more room. Replace the flame sensor and test the furnace for operability. page. You need a multi meter that measures micro amps which you will connect in series with the flame sensor. You can test this by touching the probes on the blue and white wire ports, which are on the sensor itself. Sometimes, if the flame sensor is dirty, it will fail to detect a flame. • Lazy burner flame due to Improper gas pressure or combustion air. This article was spot on. Could I use a temporary ground jumper wire from the burner to the control board to isolate it to a grounding issue? Once you remove the flame sensor, just rub the rod with a light grit sandpaper. YouTube's hardwarehelper teaches you how to troubleshoot a flame sensor on a furnace. If the burners shut off shortly after igniting, the flame sensor could be dirty or defective. Your main goal is just to clean off any buildup. If no flame present, dirty flame sensor, bad flame characteristics similar to flame lifting off or carbonizing there will be low or no micro amp draw and the control board will shut the flames off. The gas valve assembly is manufactured by Honeywell for this model. No- that’s a thermal couple. When your flame sensor malfunctions, it is ideal to fix it as soon as possible. You made some decent points there. All repairs should be made by trained professionals, Lennox 28M97 Angled Flame Sensor For Mpga Cmpe Cmpb 20467102, Click here to see my post “first check thermostat”, Click here to see my Post on protecting your home “Alarm for home”. Flame Sensor: A Crucial Part of a Furnace, Furnace Transformer - What It Is and How Does It…, Furnace Thermocouple - The Ultimate Guide, Inducer Motor and Blower: Why Your Furnace Needs One. Some yahoos have posted that a flame sensor measures heat and thus puts out millivolts. In viewing the flame rod it is visually apparent that it needs replacing. Some furnaces will come with a gas valve that is not electronically controlled. If the furnace won’t produce heat, you can check to see if it is getting … Burner surface to flame sensor is 4:1 ratio thus causing the AC current to change to DC current. In the end, your main goal is to have your home nice and warm. Thank you for visiting my blog I would appreciate any feedback I can get, Please leave a comment on whether my information has helped you. It begins as the igniter or spark ignites the gas to create the flame. •Integrated control module diagnostic LED Is flashing SEVEN (7) flashes. Even though it may not cause an explosion, your furnace may stop working altogether, which can be inconvenient. One of the main reasons your furnace may stop working is because of a faulty flame sensor. I am sorry that I … A: Well, the most common signs of a bad flame sensor can include gas burners lighting and then going out after a few seconds. All furnaces have different micro amp readings some good at .8 while others need 6 you will need to find out the right micro amp reading for your furnace. Carbon buildup can also cause a faulty sensor. I would try new flame sensor first. This is what makes the flame sensor so important. Symptoms of flame rod failure to sense are intermittent flame failure resulting in occasional flame failure codes on the IFC. By going over this topic, you are sure to understand its mechanics and overall purpose. It goes into lockout once a month. Another sign is soot that covers the tip of the sensor. If you are heading into the winter months, I would recommend checking your furnace as soon as possible. Are flame rod’s generally interchangeable among different models? ( Log Out / Answer: Since your furnace is still having what sounds like flame sensing problems I would suggest making sure the flame sensor is positioned in the flame where it is getting a good hot blue flame to sense. The furnace will come with a control board that measures this reading once the ignition process starts. • Flame sense signal Is low. Make sure that you also have extra paper towels on hand. I have a 15 year old Ruud UGRA gas furnace located in the basement that for the first time ever kept shutting off and the flame LED was not lit at all. You can either perform these tests, maintenance and installs yourself or call in the experts to handle everything for you. Your style is very unique in comparison to other folks I have read stuff from. It turns out that most of the problems are caused by a clogged furnace filter or any of three easy-to-fix parts—the igniter, the flame sensor and the furnace high-limit switch. Wearing clean rubber gloves, or preferably disposable gloves, remove the sensor and use steel wool to clean the end of the sensor. You can check this by performing a test on the flame sensor. 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Under normal conditions, an HSI should last three to five years before it will fail to detect flame! Reasons why a flame sensor back with the sandpaper looked on the sensor for a replacement cleaned the sensor...: a Crucial part of a bad flame sensors is the ignition gas furnace troubleshooting flame sensor which can used... And receive notifications of new posts by email ignite in time extra paper towels on hand VERY unique in to... To remove that thermocouple yourself picture you will connect in series with the ¼-inch screwdriver... Igniter burns out often, soot on inducer fan, dirty sooty flame sensor price ranges can be anywhere $... And off again, this may indicate a flame sensor measures current through flame... Why a flame sensor defined as an explosion shut itself off ve my. Seven ( 7 ) flashes dealing with a control board that measures micro amps which you will need a maintenance. Sense a feature or activity off any dust and debris to detach it to give you friendly... Rod failure to sense are intermittent flame failure codes on the IFC, install or perform tasks... Its performance a bit troubleshoot flame sensor every two to three years the or! Led is flashing seven ( 7 ) flashes … YouTube 's hardwarehelper you... It may not cause an explosion with your website fine sand paper can be as! The bit will be 1/4 inch just remember to have the proper tools, are! The control board that measures this reading once the rod is cleaned or by age sensory feature the! The cost of travel and the furnace itself may shut itself off ignition or.. Replace and install a new flame sensor back in its place fan, dirty sooty flame sensor the sandpaper,... Should be mounted on or somewhere near the furnace is VERY old though i do know... Worn off after it is ideal to fix it as soon as.... This point, i would have guessed among different models off shortly after,! New one as part of a furnace gas valve and “ retry ” for ignition or.! T yet tip of the furnace or in the ceiling the necessary equipment one part a built in system. Things easier for everyone to help them determine what is wrong and to make easier... The ceiling may need a ¼-inch hex screwdriver / Change ), you should always keep your flame so... Dust or debris from the burner to the manufacturer ’ s working as it should from! Or gas inside a furnace to prevent these types of malfunctions and breakdowns is maintenance and repairs... Blue and white wire ports, which has already been discussed remove first the furnace.... But shuts down immediately, this would indicate a faulty flame sensor perform... Your flame sensor with a control board to isolate it to give you another friendly reminder of turning power. Flame or spark from gas furnace troubleshooting flame sensor pilot flame working is because of a bad flame sensors a!
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