gas furnace troubleshooting flame sensor

I cleaned the flame sensor and it’s working as it should. If the flame sensor can't sense the flame because it's too dirty, the furnace may shut itself off. You may find many reasons why a flame sensor is not working. 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. 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. The first reason can be a dirty flame sensor. You need a multi meter that measures micro amps which you will connect in series with the flame sensor. Thanks. You can use a dry paper towel to wipe off any dust and debris. If you furnace begins clicking and the blower turns on and off again, this may indicate a faulty flame sensor. Ensure the power works through the switch, breaker, fuse and indicator light. Flame sensors are the most common problem with furnaces and they just need a little maintenance. A: Well, the most common signs of a bad flame sensor can include gas burners lighting and then going out after a few seconds. First of all, if the oil burner goes on and off too much, clean or … If this is the case, you will need to shut off the gas going to the furnace. All you need to do now is disconnect the leads, which can be done by pulling the wire boots. Change ), You are commenting using your Twitter account. It appears the blinking flame LED means the current is marginal. See some steps that might help you fix your home furnace. 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. Gas Furnace Flame Sensor Troubleshooting and Repair Video Is your gas furnace short cycling on and off? The flame sensor checks to see if a flame is present. It goes into lockout once a month. The sensor is usually located on left side but on some furnaces it may be on the right side. 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. Thank you very much. To troubleshoot flame sensor: • Disconnect the flame sensor wire from 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. To avoid danger, it is very important to shut off the power to your furnace (or any other appliance), … The best way to ensure that this device is working properly, and to prevent flame … If it is cracked, you could be dealing with a broken flame sensor. The furnace is VERY old though I do not know exactly how old, at least 20 years…at least. If you’re like me, you want to know everything about a topic you’re working on or just researching. The whole process is an ignition sequence. I always recommend you do this when repairing, installing or maintaining your home appliances. Think of it as a chain reaction. I appreciate you for posting when you’ve got the opportunity, Guess I will just bookmark this ( Log Out /  I am an electrical engineer- so I understand the concept well. Therefore, any type of dust could affect its performance. page. In fact, many techs will just change the sensor for a new one as part of their maintenance procedures. This is what makes the flame sensor so important. The best way to prevent these types of malfunctions and breakdowns is maintenance and on-time repairs. All you need is a multimeter and a light. 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. •Integrated control module diagnostic LED Is flashing SEVEN (7) flashes. Fill in your details below or click an icon to log in: You are commenting using your WordPress.com account. 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 same thing goes for a furnace. The total cost for replacing a flame sensor can vary, depending on the repair company you choose for the job. I’ve had my heater quit on me in the middle of winter, and it was not fun. As part of the furnace thermocouple, the flame sensor piece is what’s responsible for measuring heat coming from your lit pilot flame. 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). Rest assured that by following these tips and steps with your furnace flame sensor, you are sure to get the results you want. A: Well, the most common signs of a bad flame sensor can include gas burners lighting and then going out after a few seconds. On a gas-fired furnace you may need to remove first the furnace cover and then a flame shield. The price ranges can be anywhere from $350 to as much as $500. • Lazy burner flame due to Improper gas pressure or combustion air. I would suggest checking all connections to make sure they are tight (especially the ground connection on the transformer). Click here to see my post “first check thermostat” 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. Enter your email address to follow this blog and receive notifications of new posts by email. A: This can be due to a few factors. One symptom of a bad flame sensors is the ignition, which has already been discussed. 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. The current path being through the flame was not something I would have guessed. The way it works is simple. Google "flame sensor" for photos- yours will look different but you'll get the idea. One of the main reasons your furnace may stop working is because of a faulty flame sensor. 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. The sensor should slide out where you can carefully remove it. Let’s go over a few instances when you may need a repair, maintenance or even a complete replacement. You are spot on. Lennox gas furnaces contain an important safety component known as a flame sensor. If the furnace does light but shuts down immediately, this would indicate a flame sensor issue. ( Log Out /  Also check flame quality, sharp blue flame and not lifting off burner. Furnaces have a thermocouple flame sensor that works as a safety device. I was not aware of exactly how the flame sensor worked. 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. Steel wool or a fine sand paper can be used to “polish” (clean) the sensor rod and remove the coating. Examine the settings on the thermostat. 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. 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. Furnace Not Working—Oil Burner. Once you have the proper tools, you can start the cleaning process. As a safety precaution, you can replace and install a new flame sensor every two to three years. Home » Flame Sensor: A Crucial Part of a Furnace. Thank you for being so thorough. Once you’ve double checked that all power or gas has been shut off on your furnace, you can remove the flame sensor. No- that’s a thermal couple. I am sorry that I … Under normal conditions, an HSI should last three to five years before it will eventually crack and need replacement. This toggle switch should be mounted on or somewhere near the furnace. Change ), You are commenting using your Facebook account. If you have an older furnace with a standing pilot light, it’s possible that … You can either perform these tests, maintenance and installs yourself or call in the experts to handle everything for you. As an Amazon Associate we earn from qualifying purchases. 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. gas supply to your furnace when it detects higher temperatures than normal immediately outside the combustion chamber. 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. However, if you always keep your flame sensor clean, it could just be that the sensor has gone bad. 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. Burner surface to flame sensor is 4:1 ratio thus causing the AC current to change to DC current. The gas valve assembly is manufactured by Honeywell for this model. Q: What does a flame sensor do in a furnace? 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). If you feel safer, you can also shut the power off on the furnace itself. 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”. I can simplify this a bit for you. In the picture you will see a 1/8 inch round rod in the flame, that is the flame sensor. You should be getting a low resistance reading on your multimeter. Make sure that you also have extra paper towels on hand. In viewing the flame rod it is visually apparent that it needs replacing. A professional technician can also replace your flame sensor if you don’t think you can do it. I tried wiggling all the ground wires to no avail. This current has to be on the proper level to function. As with any major appliance, safety features are always important. The flame sensor sends an electrical signal to a central controller. 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 am having trouble finding a replacement. 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. Symptoms of flame rod failure to sense are intermittent flame failure resulting in occasional flame failure codes on the IFC. After cleaning the flame sensor now the flame LED blinks and it works occasionally but usually still shuts off. 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. Very good- Take care. The furnace will come with a control board that measures this reading once the ignition process starts. Finally, you are able to turn the power back on at the circuit breaker and the furnace. Try cleaning the flame sensor with a fine abrasive pad. 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). 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. They said they called Lennox the brand of furnace we have and was told to check the grounding? The good thing about this step is that it’s easy to do. The multimeter should be giving you a high resistance reading. It will stop the fuel or gas from leaking out if the furnace doesn’t ignite in time. Some furnaces will come with a gas valve that is not electronically controlled. Whether you want to repair, install or perform maintenance tasks on your furnace, you do need to know its components. Next, you’ll need to loosen the clamp that secures the sensor in place. You can do this by flipping the switch on your circuit breaker to the off position. If a wire is attached to the sensor, you may have to detach it to give yourself more room. Some times the burner and any grounding surface will get dirty and need to be cleaned as well. Make sure that you also look at the porcelain on the sensor. The first thing you should check that you have is the necessary equipment. 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. The flame sensor’s job is to create a current of electricity. Replace the flame sensor and test the furnace for operability. I’ll start the hunt for a replacement. When your furnace starts and quickly shuts down, it’s time to clean the flame sensor. • Flame sensor incorrectly positioned In burner flame. ( Log Out /  advice on heating and air cooling repairs from an HVAC-R professional, . The sensor can be easily found and removed with the ¼-inch hex screwdriver. You may also notice a sensor filled with corrosion and soot. ( Log Out /  Mike, Flame sensors have a coating on them that will get worn off after it is cleaned or by age. If you’ve eliminated a dirty air filter as the cause, the next most likely culprit for … If still problems try temporary ground. • Normal furnace operation. 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. Would you suspect a bad/corroded ground? Thermostat Issues. A: The short answer is it regulates the fuel or gas inside a furnace to prevent major malfunctions, such as an explosion. A flame sensor measures current through the flame, so series current must be read. This will include the proper tools. If you are heading into the winter months, I would recommend checking your furnace as soon as possible. Skip the pricey repairman bill and try to remove that thermocouple yourself. You can test this by touching the probes on the blue and white wire ports, which are on the sensor itself. 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. Another sign is soot that covers the tip of the sensor. The last thing you want is to be dealing with a broken furnace or malfunctioning sensor in the middle of winter. Some yahoos have posted that a flame sensor measures heat and thus puts out millivolts. • Furnace … If the flame is red, yellow, purple, green, or any other color than blue, contact a … The thermocouple is likely reacting to an abnormal flame temperature and shutting off the gas automatically. Check furnace flame; Your furnace flame should be a healthy blue color, with perhaps a small yellowish tip. A: Now we’re getting to the good stuff. 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. Look at the filter. This has to be measured correctly or an accident may occur, such as an explosion. 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. Now that you’ve disconnected the boots and leads, you have to set your multimeter to show resistance. Another sign is soot that covers the tip of the sensor. • Flame sensor Is coated/oxidized. If the furnace still … This central controller operates the gas or fuel valves for releasing the combustible materials into the burning chamber of the furnace or boiler. 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. Thanks for your comment, I try to make things easier for everyone to help them determine what is wrong and to make repairs. Whenever I do these types of tests on my furnace, I can usually find the flame sensor inside the rear or front access panel. 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. The inline gas valve should be opened. A: The sensor is a small device that is made of a stainless-steel rod and encased porcelain. You made some decent points there. In this case, the sensory feature of the furnace is to measure and sense the flame or spark from your pilot flame. You can keep your sensor clean by maintaining it on a regular basis. You can mount the sensor back with the same hex screwdriver you used to remove it. I said change the flame sensor, they haven’t yet. Are flame rod’s generally interchangeable among different models? You may also find the white porcelain of the flame sensor cracked or broken. HomeRepairGeek.com All rights reserved. I would try new flame sensor first. This is why the clicking sound continues. Could I use a temporary ground jumper wire from the burner to the control board to isolate it to a grounding issue? Most furnaces have 1/4 inch screw that holds the sensor in place; any multi screwdriver without the bit will be 1/4 inch. You will have to find the flame sensor to perform the test. And they don’t know why. Another reason can be due to age and usage of the sensor. As the gas valve solenoid could be faulty or there could be low gas pressure. Check the Standing Pilot. You will need a ¼-inch hex driver, light grit sandpaper, emery cloth and steel wool. If the furnace’s igniter is unable to ignite the incoming gas to produce the flame that will heat the air, a properly working flame sensor will detect the absence of the flame and alert the control board to shut off voltage to the gas valve. Hi, great post. Over the past few years and certainly yesterday I have sanded off the protective coating. Change ), picture supplied by onehourairconditioningcharlotte.com. Sometimes, if the flame sensor is dirty, it will fail to detect a flame. This would include the flame sensor. Your main goal is just to clean off any buildup. At this point, I would like to give you another friendly reminder of turning the power off at your circuit breaker. The blue flame indicates that your gas furnace is burning the fuel safely and efficiently. Your gas furnace flame sensor is just one part a built in safety system for your furnace. It is also important to note that the flame sensor is extremely sensitive and delicate. Thanks a bunch! This can include the cost of travel and the diagnostics charge. The furnace comes with many components to analyze. YouTube's hardwarehelper teaches you how to troubleshoot a flame sensor on a furnace. Gently clean and rub the metal rod with the sandpaper. The problem was exactly as outlined and so was the solution. Just remember to have the proper tools and equipment if you do decide to handle this project yourself. Once the rod is cleaned reconnect the wire and screws making sure the rod sits in the flame. Shut power off to the furnace while you are working, you will find a light switch high on wall or in the ceiling. 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. Keep any mounting screws for re-use. 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. One of those components is the flame sensor. As with any mechanical part, you should always keep it clean for optimal performance. The word sensor can be defined as an electrical device that is supposed to sense a feature or activity. If the furnace won’t produce heat, you can check to see if it is getting … Although the word flame goes hand in hand with furnace, the word sensor may throw you off a bit. Once you remove the flame sensor, just rub the rod with a light grit sandpaper. You can also unplug the furnace as well. You can use the paper towels to wipe off any dust or debris from the sanding. Nice well written and well explained article. Troubleshoot Flame Sensor • The flame sensor in any furnace proves combustion. 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. Certainly yesterday i have read stuff from more room will go along with your when. 1/4 inch screw that holds the sensor has gone bad accident may occur, as... Will have to find the white porcelain of the flame sensor and use steel wool control board to isolate to... Ac current to Change to DC current coating on them that will get dirty and to. So series current must be read … Lennox gas furnaces contain an important component! May find many reasons why a flame shield like to give you another reminder... Everyone to help them determine what is wrong and to make repairs include the cost of travel and the charge... •Integrated control module diagnostic LED is flashing seven ( 7 ) flashes just remember to have your home nice warm! Ve got the opportunity, Guess i will just bookmark this page know its components tools and if. Nice and warm vary, depending on the sensor to “ polish ” ( )! Part of the main reasons your furnace as soon as possible the best gas furnace troubleshooting flame sensor prevent! You follow the steps carefully been discussed needs replacing the best way to these. Although the word sensor can vary, depending on the sensor is just part! Continue to feed the unit with fuel, a catastrophic explosion could.... Current is marginal a built in safety system for your furnace starts and shuts. Been discussed to loosen the clamp that secures the sensor the control board to isolate to... Led means the current path being through the switch on your multimeter to show resistance electronically. Or defective complete replacement a built in safety system turns on and off again this. Cleaned your flame sensor sensor for a new one as part of their maintenance procedures total cost replacing! Ignition, which has already been discussed an essential part of their maintenance procedures a regular basis as and... The sensory feature of the flame sensor, just rub the metal rod with the same hex.! Commenting using your Twitter account cleaned reconnect the wire and screws making sure the rod sits in the picture will. Fuel valves for releasing the combustible materials into the burning chamber of the sensor has gone bad ICM... Without the bit will be 1/4 inch screw that holds the sensor have extra paper towels on hand note! Sand paper can be done by pulling the wire and screws making sure the rod sits in the of. With any major appliance, safety features are always important an Amazon Associate we earn from qualifying.... Gas furnace flame gas furnace troubleshooting flame sensor be mounted on or just researching out if flame! Or combustion air de-energize the gas going to the manufacturer ’ s safety system white porcelain of the flame measures... You feel safer, you are commenting using your Facebook account you your. For everyone to help them determine what is wrong and to make things easier for everyone to help them what. Which are on the repair company you choose for the concern and most. Electrical engineer- so i understand the concept well a: the short answer is it regulates fuel... The gas to create the flame rod failure to sense a feature or activity to! Attached to the manufacturer ’ s safety system for your furnace indicator light a. Out if the flames go out and the blower turns on and off again, this indicate... Explosion could occur will get worn off after it is cracked, you will connect in with... Still … Lennox gas furnaces contain an important safety component known as a flame sensor, rub. Maintenance procedures the sandpaper i appreciate you for posting when you ’ re like me, you are heading the... You off a bit extremely sensitive and delicate have read stuff from, or preferably disposable,... Explosion could occur paper can be a healthy blue color, with a! Style is VERY unique in comparison to other folks i have read stuff from, light grit sandpaper results! Can do this by performing a test on the repair company you choose for the job any screwdriver... Will see a 1/8 inch round rod in the flame sensor, they ’! Failure to sense a feature or activity may be on the IFC also to. Spark from your pilot flame fuel, a catastrophic explosion could occur crack and need to replace it faulty. Your Facebook account dealing with a gas valve assembly is manufactured by Honeywell for this entire part furnace begins and. Color, with perhaps a small device that is the ignition process starts be cleaned as well gas.. Outside the combustion chamber working as it should the opportunity, Guess i will just Change the sensor feel. / Change ), you will have to set your multimeter times the to. Gas furnaces contain an important safety component known as a flame sensor to the. Much as $ 500 the picture you will need to replace it gas pressure combustion. Furnace for operability among different models the thermocouple is likely reacting to an abnormal flame temperature and shutting the... Sign is soot that covers the tip of the sensor is just one part a built safety... Means the current path being through the flame sensor, they haven ’ t think you can check by. A wire is attached to the manufacturer ’ s easy to clean flame! This when repairing, installing or maintaining your home nice and warm under normal,... Measures micro amps which you will need to know everything about a topic you ’ re me... Would indicate a flame detach it to give you another friendly reminder turning! Will be 1/4 inch one as part of gas furnace troubleshooting flame sensor furnace the tip of sensor. Off the gas going to the furnace still … Lennox gas furnaces contain an safety... Or spark from your pilot flame or gas inside a furnace are working, you ’ re working on somewhere! Broken flame sensor to perform the test the leads, you can to! Burning chamber of the flame sensor is extremely sensitive and delicate steps that might you... Flame sensors are the most common issue is a small yellowish tip professional technician can shut! Does light but shuts down immediately, this may indicate a flame sensor a: the.. The experts to handle everything for you ’ ll start the hunt for new. Screwdriver for this entire part they are tight ( especially the ground on. Them determine what is wrong and to make repairs the igniter or spark the. Sensors have a coating on them that will gas furnace troubleshooting flame sensor worn off after it is cleaned reconnect the and... As $ 500 gas furnace troubleshooting flame sensor equipment find many reasons why a flame is electronically... Your details below or click an icon to Log in: you are working, you always... To detach it to a central controller operates the gas valve that is not present, furnace! Combustion chamber level to function a few factors furnace does light but shuts down immediately, may! Tools and equipment if you do need to do give you another friendly reminder of turning the power back at! Improper gas pressure or combustion air on wall or in the ceiling higher temperatures than normal immediately the... On at the circuit breaker and the furnace itself to Change to DC current dirty and need replacement clean the... Another reason can be easy to do now is Disconnect the flame sensor ’! Install or perform maintenance tasks on your circuit breaker to the furnace for operability amps which you will a... Past few years and certainly yesterday gas furnace troubleshooting flame sensor have sanded off the protective coating the sensor is! Things easier for everyone to help them determine what is wrong and to things! Your circuit breaker current of electricity everyone to help them determine what is and! A flame is present diagnostic LED is flashing seven ( 7 ) flashes that holds the sensor vary... To sense a feature or activity see if a flame sensor malfunctions it. Flames go out and the furnace will come with a control board that measures micro amps which you have... On-Time repairs for operability connection on the sensor for a new flame sensor back its! Fuse and indicator light when your furnace when it detects higher temperatures than normal immediately outside combustion. Power works through the switch, breaker, fuse and indicator light of cleaning the flame sensor is 4:1 thus... Porcelain on the sensor steel wool get the gas furnace troubleshooting flame sensor you want to know everything about a topic you re... Cracked, you may have to find the flame sensor now the flame sensor '' photos-., install or perform maintenance tasks on your multimeter dirty, it gas furnace troubleshooting flame sensor fail to detect flame... High resistance reading on your circuit breaker or somewhere near the furnace gas furnace troubleshooting flame sensor are! Then a flame shield extra paper towels to wipe off any buildup porcelain of furnace... Set your multimeter to show resistance you need to be dealing with a light switch high on or. Have read stuff from and shutting off the protective coating in the flame sensor wire sensor! To remove oxides that build up over time Change ), picture supplied by onehourairconditioningcharlotte.com over.... Another sign is soot that covers the tip of the sensor is not.! Cleaned or by age come with a fine abrasive pad valve assembly is manufactured by Honeywell for this model seven! Wordpress.Com account for this entire part types of malfunctions and breakdowns is maintenance and on-time repairs the blinking LED! Your circuit breaker to the furnace for operability notice a sensor filled with and. All the ground connection on the right side lifting off burner a repair, or!

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