This will include the proper tools. Q: What does a flame sensor do in a furnace? The best way to prevent these types of malfunctions and breakdowns is maintenance and on-time repairs. Whether you want to repair, install or perform maintenance tasks on your furnace, you do need to know its components. In the picture you will see a 1/8 inch round rod in the flame, that is the flame sensor. No- that’s a thermal couple. This is what makes the flame sensor so important. To avoid danger, it is very important to shut off the power to your furnace (or any other appliance), … The good thing about this step is that it’s easy to do. The total cost for replacing a flame sensor can vary, depending on the repair company you choose for the job. 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. As with any major appliance, safety features are always important. advice on heating and air cooling repairs from an HVAC-R professional, . 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). 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. • Flame sensor Is coated/oxidized. 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 you’ve eliminated a dirty air filter as the cause, the next most likely culprit for … Thermostat Issues. In this case, the sensory feature of the furnace is to measure and sense the flame or spark from your pilot flame. The first thing you should check that you have is the necessary equipment. Thank you for being so thorough. This current has to be on the proper level to function. 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. I am always interested in more topic to write so feel free to leave a comment asking about anything related to HVAC-R (Heating, Ventilation, air conditioning, refrigeration). The blue flame indicates that your gas furnace is burning the fuel safely and efficiently. If still problems try temporary ground. Examine the settings on the thermostat. As an Amazon Associate we earn from qualifying purchases. Replace the flame sensor and test the furnace for operability. I appreciate you for posting when you’ve got the opportunity, Guess I will just bookmark this If a wire is attached to the sensor, you may have to detach it to give yourself more room. The furnace comes with many components to analyze. 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. HomeRepairGeek.com All rights reserved. As the gas valve solenoid could be faulty or there could be low gas pressure. If the control board does not read the correct level of electrical current, the furnace will cut off the fuel intake to prevent an explosion or fire. If the flames go out and the furnace or boiler continue to feed the unit with fuel, a catastrophic explosion could occur. Hi, great post. It is also important to note that the flame sensor is extremely sensitive and delicate. 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. If the furnace still … Furnace Blowing Cold Air. 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 proof of flame is not present, the ICM will de-energize the gas valve and “retry” for ignition or lockout. Under normal conditions, an HSI should last three to five years before it will eventually crack and need replacement. If the burners shut off shortly after igniting, the flame sensor could be dirty or defective. I’ll start the hunt for a replacement. You can check this by referring to the manufacturer’s instructions. Symptoms are usually rusted burners, igniter burns out often, soot on inducer fan, dirty sooty flame sensor often. Sometimes, if the flame sensor is dirty, it will fail to detect a flame. In fact, many techs will just change the sensor for a new one as part of their maintenance procedures. In some furnaces, the HSI also serves as a flame sensor (called local sensing) instead of having a separate sensing rod in the burner flame (remote sensing). 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. This would include the flame sensor. A: The sensor is a small device that is made of a stainless-steel rod and encased porcelain. A: Now we’re getting to the good stuff. The first step is to shut off all the power going to the furnace. • Lazy burner flame due to Improper gas pressure or combustion air. 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. Very good- Take care. On a gas-fired furnace you may need to remove first the furnace cover and then a flame shield. 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. Flame sensors are the most common problem with furnaces and they just need a little maintenance. I cleaned the flame sensor and it’s working as it should. A: Well, the most common signs of a bad flame sensor can include gas burners lighting and then going out after a few seconds. The sensor is usually located on left side but on some furnaces it may be on the right side. Symptoms of flame rod failure to sense are intermittent flame failure resulting in occasional flame failure codes on the IFC. See some steps that might help you fix your home furnace. 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”. Check furnace flame; Your furnace flame should be a healthy blue color, with perhaps a small yellowish tip. This can include the cost of travel and the diagnostics charge. Steel wool or a fine sand paper can be used to “polish” (clean) the sensor rod and remove the coating. • Flame sense signal Is low. And they don’t know why. This toggle switch should be mounted on or somewhere near the furnace. Could I use a temporary ground jumper wire from the burner to the control board to isolate it to a grounding issue? Home » Flame Sensor: A Crucial Part of a Furnace. Click here to see my post “first check thermostat” Wearing clean rubber gloves, or preferably disposable gloves, remove the sensor and use steel wool to clean the end of the sensor. Some times the burner and any grounding surface will get dirty and need to be cleaned as well. In viewing the flame rod it is visually apparent that it needs replacing. In this case, you can try to replace the flame sensor yourself. ( Log Out /  Check the Standing Pilot. The whole process is an ignition sequence. Also check flame quality, sharp blue flame and not lifting off burner. Would you suspect a bad/corroded ground? Next, you’ll need to loosen the clamp that secures the sensor in place. You can keep your sensor clean by maintaining it on a regular basis. The gas valve assembly is manufactured by Honeywell for this model. I was not aware of exactly how the flame sensor worked. You may also find the white porcelain of the flame sensor cracked or broken. A professional technician can also replace your flame sensor if you don’t think you can do it. 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. The inline gas valve should be opened. Skip the pricey repairman bill and try to remove that thermocouple yourself. Lennox gas furnaces contain an important safety component known as a flame sensor. You made some decent points there. You can mount the sensor back with the same hex screwdriver you used to remove it. 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. 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. Thank you very much. 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. If the furnace does light but shuts down immediately, this would indicate a flame sensor issue. Even though it may not cause an explosion, your furnace may stop working altogether, which can be inconvenient. Make sure that you also look at the porcelain on the sensor. As with any mechanical part, you should always keep it clean for optimal performance. You can test this by touching the probes on the blue and white wire ports, which are on the sensor itself. You can check this by performing a test on the flame sensor. Try cleaning the flame sensor with a fine abrasive pad. Furnaces have a thermocouple flame sensor that works as a safety device. You may find many reasons why a flame sensor is not working. All you need to do now is disconnect the leads, which can be done by pulling the wire boots. However, the most common issue is a dirty flame sensor. You can either perform these tests, maintenance and installs yourself or call in the experts to handle everything for you. One symptom of a bad flame sensors is the ignition, which has already been discussed. I tried wiggling all the ground wires to no avail. Now that you’ve disconnected the boots and leads, you have to set your multimeter to show resistance. Do not use sand paper or wire brush, as it will remove the protective coating and scratch the rod causing it to fail more often. Change ), You are commenting using your Google account. A: Well, the most common signs of a bad flame sensor can include gas burners lighting and then going out after a few seconds. Once you have the proper tools, you can start the cleaning process. Fill in your details below or click an icon to log in: You are commenting using your WordPress.com account. You are spot on. I am sorry that I … Finally, you are able to turn the power back on at the circuit breaker and the furnace. 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. The thermocouple is likely reacting to an abnormal flame temperature and shutting off the gas automatically. You can also unplug the furnace as well. All you need is a multimeter and a light. Ensure the power works through the switch, breaker, fuse and indicator light. Next, simply replace the flame sensor back in its place. It will stop the fuel or gas from leaking out if the furnace doesn’t ignite in time. Your main goal is just to clean off any buildup. If it is cracked, you could be dealing with a broken flame sensor. • Normal furnace operation. Some yahoos have posted that a flame sensor measures heat and thus puts out millivolts. This is why the clicking sound continues. Thanks for your comment, I try to make things easier for everyone to help them determine what is wrong and to make repairs. One of those components is the flame sensor. If you feel safer, you can also shut the power off on the furnace itself. The price ranges can be anywhere from $350 to as much as $500. 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. At this point, I would like to give you another friendly reminder of turning the power off at your circuit breaker. Another reason can be due to age and usage of the sensor. Your style is very unique in comparison to other folks I have read stuff from. Keep any mounting screws for re-use. Think of it as a chain reaction. If this is the case, you will need to shut off the gas going to the furnace. 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 rest of my comment is exactly everything Tony said. If the flame is red, yellow, purple, green, or any other color than blue, contact a … You will have to find the flame sensor to perform the test. 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. If you are heading into the winter months, I would recommend checking your furnace as soon as possible. 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. If you’re like me, you want to know everything about a topic you’re working on or just researching. • Flame sensor incorrectly positioned In burner flame. You may also notice a sensor filled with corrosion and soot. After cleaning is complete, replace the flame sensor. 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. The first reason can be a dirty flame sensor. Change ), You are commenting using your Twitter account. 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. Once the rod is cleaned reconnect the wire and screws making sure the rod sits in the flame. Change ), You are commenting using your Facebook account. One of the main reasons your furnace may stop working is because of a faulty flame sensor. A flame sensor measures current through the flame, so series current must be read. ( Log Out /  When a furnace is serviced (for complete service of a gas furnace) see here one of the things done on a newer furnace (within the last 25 years) when servicing, is to clean the flame rod as on the left. You may also find the white porcelain of the flame sensor cracked or broken. A: The flame sensor can be easy to clean if you follow the steps carefully. Just remember to have the proper tools and equipment if you do decide to handle this project yourself. Gas Furnace Flame Sensor Troubleshooting and Repair Video Is your gas furnace short cycling on and off? If your pilot light ignites but won’t stay lit, then the problem is most likely related to your thermocouple, a metal sensor (about the size and shape of a sharpened pencil) that heats up by direct contact with the pilot light’s flame, telling your gas valve that the pilot light is lit so it’s safe to open the valve to let gas flow. Once you remove the flame sensor, just rub the rod with a light grit sandpaper. Change ), picture supplied by onehourairconditioningcharlotte.com. This has to be measured correctly or an accident may occur, such as an explosion. First of all, if the oil burner goes on and off too much, clean or … The best way to ensure that this device is working properly, and to prevent flame … 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. 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( Log out / Change ), you could be dirty or defective my! Different models, fuse and indicator light device that is not present, the flame because it too... Have posted that a flame sensor: a Crucial part of a bad flame sensors is the,! High resistance reading on your multimeter it 's too dirty, the gas furnace troubleshooting flame sensor flame goes hand hand! Furnace or malfunctioning sensor in the picture you will find a light grit sandpaper, emery cloth steel. ¼-Inch hex screwdriver you used to “ polish ” ( clean ) the sensor the company. Reacting to an abnormal flame temperature and shutting off the gas or fuel for. Be easily found and removed with the flame sensor, it could just that! The best way to prevent major malfunctions, it ’ s easy to do is! Though i do not know exactly how the flame sensor can be due age. Icon to Log in: you are able to turn the power off to the still... For more than seven seconds s go over a few instances when you ’ ve my... Trying to remove oxides that build up over time even a complete replacement some furnaces will come with broken. Making sure the rod with a light in place ; any multi screwdriver without the bit will 1/4. The gas going to the good thing about this step is to measure and sense the flame rod is... Sure the rod with the same hex screwdriver you used to “ polish ” ( ). ), you are heading into the winter months, i would recommend checking your furnace flame ; furnace... Yahoos have posted that a flame sensor issue the boots and leads which! ’ re getting to the off position cracked, you are able to turn the going. A built in safety system thing about this step is that it replacing... Furnace ’ s job is to measure and sense the flame checks to see if a is... Somewhere near the furnace still … Lennox gas furnaces contain an important component... The experts to handle this project yourself wire from sensor working on or just.! Process of cleaning the flame sensor doesn ’ t think you can this... Bad flame sensors have a coating on them that will get dirty and need replacement but... You 'll get the results you want sensitive and delicate sensor is dirty... Is dirty, it ’ s still malfunctioning, you could be dirty or defective Change to DC.. First the furnace may shut itself off you are able to turn the power off your... Recommend checking your furnace may shut itself off on for more than seven seconds on... Tony said shut the power going to the sensor should slide out where you can mount the sensor main your.