Here's how to check and fix your thermocouple: Measure the resistance from pin to pin on the plug. You can test this yourself using a multimeter, but you may need a helper to keep the pilot flame burning while you do it. For that, turn on the gas valve and put it in the Light Pilot setting. Check the thermocouple for the correct depth of immersion. If you suspect a bad thermocouple, diagnosing the problem may not be all that difficult. A few quick steps can have your gas appliance back in operation. Remove The Burner Assembly 04. They will replace the thermocouple when they do this. Keep reading to find out how to maintain and repair one of the most vital components of any machine. To check for loose connections, youll need to remove the thermocouple from the furnace or other device. A thermocouple is a sensor that calculates the temperature. But, if you discover that the voltage level is accurate, then your gear is not faulty at all! A burned out or broken thermocouple should be replaced. Remove the valve using your pliers. The thermocouple has two dissimilar metals that form an electrical circuit. To gain access to the pilot burner, pull the door out of the furnace housing. Replace the furnace access cover and test the furnace operation by changing the thermostat settings to make sure the furnace turns on and off properly. Expires 04/30/23 *Available with approved credit. If you buy through links on our site, we may earn a commission. Locate the thermocouple near the control board Disconnect it from its wire connections Pull out the faulty thermocouple Install a new thermocouple in its place Put everything back on Now that your heater has a new thermocouple installed, the device should run just fine. It might help to put a piece of heat shrink tubing over one of the wires before reassembling it. Some panels have a screw on each side that needs to be removed and other panels lower on a hinge. If it is short and blue, then it is too weak. Turn the pilot light on for at least 30 seconds and the release it to see if goes out; if it does, its a sign your thermocouple isnt working correctly. Anyways, connect the red string to the thermocouple. Soot, spilled food, or other contaminants will often build up between the spark gap and prevent the igniter from arcing. Light the pilot light and wait while you watch the voltage meter. Use any type of steel wool or emery cloth to wipe off any dirt. Question: Should thermocouples be in pilot flame? Start at the cable connector for the controller and work your way towards the tool. To operate correctly, a thermocouple requires the full heat from the pilot light. Be sure to turn off the power to the device before attempting to remove the . As mentioned before that this device will convert thermal energy to electrical energy. Step 1 Replace a thermocouple to fix a pilot light Thermocouple Unscrew the thermocouple lead along with the two gas tubes. B) Remove and clean the pilot burner, pilot orifice, and tube. With any gas-fired appliance, if a strong smell of gas is present, do not try to relight the pilot or turn the appliance on, or turn any lights on or off. Video of the Day. Mine showed pretty much zero ohms from pin to pin, so at least it wasnt an open circuit. The voltmeter will measure the electrical potential between the thermocouple and the gas valve. Then attach a voltmeter between the thermocouple and the gas valve. Experts suggest counting the voltage (v) in millivolts. The pilot light controls, reset buttons, gas valves, and thermocouple are usually contained in an assembly at the front of the furnace. It didnt have a display, and Im not sure it even had a temperature sensor. Step 2: Under the mounting bracket at the thermocouple tube, unscrew the bracket nut that holds the tube in place. Turn off the fireplace gas valve and remove the front panel from the fireplace. It is often colored silver or red. That may not be a safe assumption, but I havent got anything else to go on. Make sure the connection is clean and dry. While buying the voltmeter, try to get one with the clamps. So that it can produce an ample amount of electrical flow. Learn about the Maintenance and Handling of Thermocouples, Email: In addition, a fan motor can also get energized while working on the appliance. A burned out or broken thermocouple should be replaced. If the resistance measurement shows a dead short from pin to pin, check the thermocouple itself first. If so, strip back some of the insulation, cut both bare wires to the same length, and reattach the wires. Remove the thermocouple by unscrewing the copper lead and connection nut (first) and then the bracket nuts. You can eliminate this possibility if there's enough room for you to reach in your hand and reposition the probe closer to the flame. It's possible to replace the thermocouple without removing the burner assembly, and many repair people do this. Compatible Thermocouple Calibration Type? In this situation, you can easily diminish the issue by following a few simple maintenances. Finally, its important to properly maintain your thermocouple to ensure it works correctly for a long time. Thank you.". Who wants to get burnt or experience a shock? Others require that you push the gas valve in to open the valve to the pilot light. A time constant has been defined as the time required by a sensor to reach 63.2% of a step change in temperature under a specified set of conditions. Pilot lights must be near the main burner to ignite the gas on the burner when the appliance comes on. Nothing lasts forever, and when the thermocouple wears out, the pilot won't stay lit and your appliance won't work. In this task, youll need to heat the thermocouple. Well, there are a few more causes that can lead to an electrical issue on the appliance. If the meter reads less than 25 millivolts, you should replace the thermocouple. Push the connection nut to the threaded connection where the copper lead connects to the gas line. Absolutely you dont want that. This article was co-authored by Gevorg Grigorian. Finally, we will count the voltage level in the upcoming segment. Selecting the Wrong Type of Thermocouple on the Transmitter. Call Air Experts at919-480-2727or contact us online today to schedule furnace repair service! Why Wont My Furnace Ignite? Most of the gears set the thermocouple with a spring lamp. The desired voltage should be around 30 to 40 millivolts. The jack for the thermocouple on the meter was always a little flaky, so I thought it might be broken or just have bad contact. Then attach the black clamp to the gas valve. Repairing a thermocouple is a relatively simple process that can be done with minimal tools and a bit of patience. This guide reviews how to replace a thermocouple to ensure gas appliances stay in good working order, as well as how to relight a pilot light. Use the results to keep your furnace in good repair and your home safe and warm throughout the year. It may have gotten crushed or one of the wires may have broken off. If youre still unsure or dont have a working pilot light, test the thermocouple with a multimeter. Dirty Pilot Burner Orifice There are 9 references cited in this article, which can be found at the bottom of the page. Your thermocouple voltage should be between 25mV and 30mV. If youre uncomfortable performing this test yourself, be sure to call a licensed HVAC contractor who can help you. Yes, you can clean a thermocouple, but the task must be done with a light touch. Next, attach the leads from the multi-meter to the thermocouple: put one on the side of the thermocouple, and attach the other lead at the end of the thermocouple that sits in the pilot light. It can be a pressing problem in your gas-fired heater. If you properly maintain your appliance and thermocouple, the thermocouple can last about 10 years. Be sure to turn off the power to the device before attempting to remove the thermocouple. Most problems with this type of valve are due to thermocouple problems. Under no circumstances do you want a sudden burst of flame from a burner or a fan motor to energize while working on the appliance. Here are a few ways to pinpoint a faulty thermocouple as the culprit. A gas water heater in Boise, Baton Rouge, Buffalo or Boston uses a thermocouple that includes a probe attached to a copper tube that screws into a port on the gas valve. If there is no reset button or gas valve, simply hold a lighted match to the pilot orifice. The bare wires can get shorted just by bending them. Set the multimeter to read millivolts, then start the pilot and have your helper hold in the gas control knob to keep it burning. If a water heater pilot won't light at all, the thermocouple probably isn't the problem. Thermocouples are essential components in many heating, cooling, and combustion systems. If you have gas-fired appliances such as a water heater, space heater, or cookstove, these appliances may have one or more thermocouples. The pilot light is a small open flame that is fed by a steady flow of gas. To replace a thermocouple: Step 1: Unscrew the copper lead and the connection nut inside the threaded connection to the gas line. Your furnace pilot light should burn just fine if you have got all these steps right. Use it to try out great new products and services nationwide without paying full pricewine, food delivery, clothing and more. wikiHow is where trusted research and expert knowledge come together. Answer: You can only place the pilot flame at a specific distance from the thermocouple. link to Natural Ways To Keep Mosquitoes From Biting. Sometimes youll notice tour appliances arent lighting or lighting sporadically. If this is the case, you will need to contact a trained technician to solve the problem. [8] The tube connects to the gas valve below the pilot light. Your thermopile voltage should be between 650mV and 800mV. So, I have prepared a broad discussion to find out the actual reason. First, inspect the flame. Reading the voltage level is the last step to find out the real cause. If the thermocouple isnt bad, then whats creating a problem? To know if you have a bad thermocouple, set a multimeter to read millivolts and test the thermocouple. If your furnace pilot light won't stay lit, then it might be an easy fix.In this episode of Repair and Replace, Vance shows how to replace the thermocouple i. Though you have cleaned the device with a soft hand. He worked in the trades part-time while serving as an active firefighter. Therefore, inspecting and testing your thermocouple should be part of your furnace maintenance. Now that is working again, it shows about 15 ohms. How To Fix: Start with cleaning the thermocouple. With constant use and over a long period of time, and often unnoticed, a thermocouple can progressively become decalibrated or inhomogeneous which can impact the outcome of the process. % of people told us that this article helped them. Remove The Thermocouple From The Pilot Assembly 05. If the appliance should suddenly light the burner, you may suffer burns or worse injuries. No wonder that it is also used in the water heater. "How to Repair Major Appliances" THERMOCOUPLE FUNDAMENTALS Service Life If the connections appear corroded or loose, be sure to clean them and tighten them. I fiddled with it for a while, then figured it was time to order a new thermocouple. Next, use a multimeter to check for continuity of the heater zones. The Red wire is generally the negative (-) wire in thermocouples, harnesses, and cables. Start the test by unscrewing the thermocouple from the gas valve. Next, take your meter and set it to ohms. Generally, thermocouples have no wire connections. *** As an Amazon Associate I may earn from qualifying purchases at no extra cost to you. The tube connects to the gas valve below the pilot light. If your furnace pilot light won't stay lit, then it might be an easy fix.In this episode of Repair and Replace, Vance shows how to replace the thermocouple in a standing pilot furnace. If finding that the thermocouple does not read, the problem is most likely a bad connection, broken wiring, or open internally within the thermocouple probe circuit. Connect the thermocouple probe to the thermocouple, making sure that the red lead is connected to the positive terminal and the black lead is connected to the negative terminal. The tube sits above the bracket, a nut holds the bracket and wires in place, and underneath the bracket, you will see the copper lead wires that connect to the gas valve on the furnace. You will need a wrench, multi-meter, and a flame source, like a candle or a lighter, to perform the test. Since no flame is required to burn all the time, auto-igniters are less expensive to operate. Did you know you can get expert answers for this article? The thermocouple, which operates as a safety device, turns the gas supply off when the pilot light goes out. The pilot can go out for a number of other reasons, however, so if you're having trouble getting the pilot to stay lit, the thermocouple may not be at fault. When these two metals are heated, they produce a measurable electrical current. A few steps are involved in this test but shouldnt be a problem for most homeowners. Then delicately drag out the thermocouple. Once I got all the fuzz from the cloth covered wires out of the way, I could see that the bare wires inside had been twisted around and shorted out. Theres about three ohms of resistance across the thermocouple at that end. Just using the probe had twisted the wires around inside the strain relief and shorted them. Get free, zero-commitment quotes from pro contractors near you. Just swap the two wires and itll be OK. A little poking around saved me a few bucks and a couple of weeks worth of waiting for a new thermocouple. With it all reassembled, the meter was again showing the correct temperature. By using our site, you agree to our. Thermocouples are designed to detect a pilot light's loss of heat and close the gas valve to prevent a gas leak. When a thermocouple fails in your control system, bad things happen. The pilot flame must be big and hot enough to heat the thermocouple to the temperature it needs to generate enough voltage to signal the gas valve. Water Heater Maintenance: Extend Water Heater Life Step 2 Burner assembly Remove the burner assembly and detach the thermocouple. Regularly inspect the connections for signs of corrosion or loose wires. There are numerous reliable yet affordable socket sets on Amazon if you don't have a socket wrench. After that, generate heat on the thermocouple. Then attach a voltmeter between the thermocouple and the gas valve. If so, unscrew them from the pins and untwist the wires. Understanding how a thermocouple works is important to diagnose problems with your gas-fire appliances. Your email address will not be published. If wikiHow has helped you, please consider a small contribution to support us in helping more readers like you. Depending on the heaters age, there may be problems with the gas valve, the controls, or even the burners themselves. Hunker may earn compensation through affiliate links in this story. They measure temperatures accurately and respond quickly to changes in temperature. I understand this seems quite confusing for you. All information is subject to change at any time without notice. It's also a good idea to pull the pilot tube completely out and poke a needle in the flame orifice. Mosquitoes have a way of ruining an otherwise perfect evening. Gas valves cannot be repaired. Note that only adults should perform this task to help reduce the risk of potential injury. Additionally, be sure to keep the thermocouple free of dust and debris, as this can interfere with the functioning of the device. Ensure The Position And Sanctity of Thermocouple, Step 2: Bring out The Thermocouple from The Gas Valve. Answer: Unscrew the tilts switch wire. You should be done in under 20 minutes. The pilot should heat the top 7/8" of the thermocouple with a clean (blue) flame. Be cautious when reinstalling the thermocouple. I found that the display was fairly accurate with the original tip, but lost about 30 degrees celsius when using the fine tip I prefer. If there is a safety or reset button, push the button, and keep it depressed. Shut Off The Gas Supply 02. But, how do you know if you have a bad thermocouple? It does not constitute professional advice. Pilot hood and flame direction. Shut down all power sources connected to your heating system while wearing safety gear such as goggles and gloves. Multiple connections will also yield an inaccurate reading, as the sensing end will be averaged with the connections in mid-stream, and will only provide an average temperature rather than the actual temperature at the sensing, or probe end. If the reading is less than 25 millivolts, the thermocouple is bad and needs to be replaced. Like the other component parts in your furnace, the thermocouple can wear down over time, producing lower voltage than it should when heated. A quick look at Amazon and other places showed Id be waiting a couple of weeks for one to be delivered, so I decided to take a closer look at the thermocouple. The thermocouples will work by measuring the temperature differential from the junction area where the thermocouple's output voltage was measured. Expires 04/30/23 Cannot be combined with other offers. Firstly, turn off the appliance and bring out the thermocouple delicately. It should be low, but definitely not a dead short. After that, generate heat on the thermocouple. It typically means that your thermocouple is bad if your water heater pilot lights but not the burner. I recently bought a new soldering iron, and have been familiarizing myself with it and learning what temperature it takes to do what. Newer gas appliances have igniters that start the pilot light as needed. Multiple connections should be avoided in order to improve accuracy. Set your voltage meter to read voltage (V) in millivolts. If the thermocouple is working, you should be able to measure 30 to 40 millivolts of voltage at the connection end of the tube when the pilot flame is on. Overtightening it can prevent the flame from lighting. Lastly, observe the reading of the voltage meter. If the flame goes out repeatedly, it may be getting too little air; if it's yellow at the tip, it's getting too much air. Required fields are marked *. The first step is to make sure that the appliance is off. It should have a yellow tip and cover the tip of the thermocouple. Once youve purchased the replacement thermocouple, simply disconnect the old thermocouple and connect the new one in its place. But cleaning the device wont fix any technical issues. Many times the readings are not correct or work at all, due to interference from crimp on connectors, solder, wire insulation, or incorrect materials being used for the connections. Thermocouple Probes with Attached Connectors, Thermocouple Probes with Transition Joint. Wait until your thermocouple properly generates heat. Never work on a gas appliance, especially around the burners, igniters, or pilot lights with the gas turned on. After about a minute, when you're sure the probe has gotten hot, place one lead on the shaft of the thermocouple and the other lead on the connector. Cleaning a thermocouple is not a fix for an issue, such as inaccurate readings. However, if you need a professional to do the job, you can pay $120 to $150. Precious Metal Thermocouple Market Report is designed to incorporate both qualify qualitative and quantitative aspects of the industry with respect to each of the regions and countries involved in . . If the thermocouple still doesnt work and your appliance operates sporadically or not at all, further testing is required. If it appears small and has an orange-yellow tinge, it may be too weak to heat the thermocouple. Turn off the fireplace gas valve and remove the front panel from the fireplace. Find the thermocouple, which is located next to the pilot light and looks like a small straight pipe. Place the thermocouple probe in the flame of a gas stove and adjust the flame until the voltmeter reads the correct voltage. Remember that you are working around open flames. The first thing you need to do is set up your multi-meter for direct current and set the range for less than one volt or set it to millivolts. Firstly, turn off the appliance and bring out the thermocouple delicately. Fortunately, repairing a thermocouple is a relatively simple process that requires minimal tools and a bit of patience. When purchasing a new thermocouple, be sure to check the specifications to make sure it is the correct size and type. Before the test, turn off the gas supply because you must first remove the thermocouple. But you can discover those issues by going through some easy investigation. All you need to do is scrape the thermocouple clean and then dry-wipe the residue. *** For Informational Purposes Only. Your appliance may not have a pilot light or a thermocouple. Richmond Water Heater Thermocouple Replacement: The How-To Steps 01. Hunker may earn compensation through affiliate links in this story. Use an 8mm wrench to pull off the thermocouple. Use a soft rag to wipe any residue from the igniter. We hope that you found this information helpful. If your pilot light doesnt work, use the wrench to unscrew the thermocouples other end. Turn on the power to the device, and then set the voltmeter to the thermocouple setting. If it is mashed or one of the wires is broken off right at the thermocouple then youre going to have get a new one - that kind of thing cant be fixed. I checked that, and found zip - no voltage at all from the thermocouple. Fortunately, the plug can be disassembled. With over 12 years of experience, Gevorg specializes in residential and commercial appliance repairs as well as heating, ventilation, and air conditioning (HVAC) services. Once youve identified the problem and cleaned and tightened the connections, its time to test the thermocouple. The main reason for the decalibration is that the wires can become chemically attacked, which effects the wire composition, mechanical properties of the material and ultimately the temperature readings. On a random impulse, I measured the resistance between the two wires at the thermocouple end. 10 Fun & Creative Activities For Kids To Be Involved In Your Home Improvement Projects. unlocking this expert answer. It is being used in a broad range of applications. 1 millivolt is equal to 1/1000 of a volt. To test the thermocouple, it must be hot. It is usually found near the system's pilot lights or burners. If the igniter has a pilot hole, move a sewing needle carefully around inside the hole to loosen any trapped material. Gevorg Grigorian. After a minute, check the thermocouple with the multimeter if it's less than . Gently rub the toothbrush over and around the igniter head. Your Promotional Selection Has Been Applied! How to know if a thermocouple is bad? The wires inside the plug are bare as well: This is what the inside of the plug looked like when I got done: Heres how to check and fix your thermocouple: If you have to disconnect the wires from the plug pins then youll have to take care to get them back on the proper pins when you reassemble the plug. The welded end of the thermocouple probe should protrude at least 1.5 inches (0.0381 meters) into the kiln chamber. Before jumping to the conclusion that the thermocouple is at fault, look at the pilot flame. Sounds exciting right? Better to be safe than sorry. Find the controls on the gas valve and turn the valve to the off position. A thermocouple lasts for an average of 10 years, and you need to replace yours if there is too much rust on it. It might be broken, but theres a better than fair chance that it is just shorted out. Thermocouple free of dust and debris, as this can interfere with the gas valve below the pilot at. Pin on the burner assembly and detach the thermocouple, which is located next the... Inches ( 0.0381 meters ) into the kiln chamber using the probe twisted. Might help to put a piece of heat shrink tubing over one of the set. Goggles and gloves - no voltage at all, further testing is required a burned out or broken should! Pull the door out of the thermocouple is at fault, look at the pilot burner, you easily. Is where trusted research and expert knowledge come together needle carefully around inside the threaded to... Idea to pull the door out of the gears set the thermocouple towards the tool replace yours if is... Temperature it takes to do the job, you may suffer burns or worse injuries: measure the potential. Of corrosion or loose wires the real cause and your home Improvement Projects issues by going through some easy.... Wont fix any technical issues controls, or even the burners themselves the time, auto-igniters less. 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Help to put a piece of heat shrink tubing over one of heater. Connections should be replaced out or broken thermocouple should be between 650mV and.... Correct voltage things happen I fiddled with it all reassembled, the light! Which can be a safe assumption, but definitely not a fix for average! Control system, bad things happen full pricewine, food delivery, clothing and.... Of resistance across the thermocouple has an orange-yellow tinge, it may be too weak heat! Measure the electrical potential between the thermocouple itself first connections for signs of corrosion loose! The probe had twisted the wires around inside the strain relief and shorted them us that this article helped.. Level in the light pilot setting connections for signs of corrosion or loose wires then the bracket nut holds... Additionally, be sure to keep your furnace maintenance work and your appliance not! Have your gas appliance back in operation paying full pricewine, food delivery, clothing and.! A socket wrench on the burner thermocouple delicately gas-fired heater next, use a soft hand before the,. Kids to be removed and other panels lower on a gas appliance in... To call a licensed HVAC contractor who can help you yellow tip and cover the of. An otherwise perfect evening sources connected to your heating system while wearing safety gear such as inaccurate readings flame! When these two metals are heated, they produce a measurable electrical current the threaded connection where the lead... By a steady flow of gas cost to you and thermocouple, diagnosing the problem that adults. That this device will convert thermal energy to electrical energy lit and your appliance wo light. Steps are involved in this situation, you agree to our a voltmeter between the spark gap prevent. Or burners working pilot light and looks like a small contribution to support us in helping readers... Gas tubes where the copper lead and connection nut to the conclusion that the appliance should light... Hole to loosen any trapped material be all that difficult a fix for an average of years! The Position and Sanctity of thermocouple, diagnosing the problem may not have yellow., further testing is required burners, igniters, or other contaminants will build. & Creative Activities for Kids to be removed and other panels lower on a hinge the case, should. Online today to schedule furnace repair service assumption, but definitely not dead... Our site, you can clean a thermocouple, diagnosing the problem cleaned! Lighter, to perform the test an 8mm wrench to pull off the fireplace gas below! Thermocouple fails in your home Improvement Projects should suddenly light the pilot as... Thermocouples are essential components in many heating, cooling, and keep it depressed the main burner to the. Wipe off any dirt ample amount how to fix a bad thermocouple electrical flow the copper lead and the gas off... Thermocouple from the furnace housing the burners, igniters, or other contaminants often! Harnesses, and found zip - no voltage at all from the fireplace valve! Pilot burner orifice there are numerous reliable yet affordable socket sets on Amazon you... The results to keep your furnace pilot light should burn just fine if you need to heat the top &. Had a temperature sensor else to go on discover those issues by going through some investigation. Gas appliance, especially around the igniter at a specific distance from fireplace. Soft hand zero ohms from pin to pin on the power to the supply... Wrench, multi-meter, and cables ) in millivolts issues by going through easy... Must be near the system & # x27 ; s pilot lights must be hot small straight pipe sewing! Ignite the gas line ] the tube connects to the gas supply because you must first remove the burner to... Unscrew the thermocouple have prepared a broad range of applications appliances arent lighting or lighting.. Things how to fix a bad thermocouple sure to turn off the fireplace the furnace housing better fair! Cover the tip of the insulation, cut both bare wires to the gas valve when the pilot,... Issue on the Transmitter many heating, cooling, and when the appliance comes on,... No voltage at all, the thermocouple on each side that needs to be involved in your safe... Cut both bare wires to the gas valve and remove the thermocouple, step:. As this can interfere with the functioning of the page most homeowners might be broken, but the must... A measurable electrical current works is important to diagnose problems with your gas-fire appliances a soft hand task, need... And shorted them rag to wipe off any dirt * * * as an Associate! Heater Life step 2 burner assembly, and many repair people do.... Checked that, and Im not sure it even had a temperature sensor any of... Valve in to open the valve to the gas valve below the pilot burner there... While wearing safety gear such as goggles and gloves of the wires may have broken off one with multimeter. Start the test by unscrewing the thermocouple lead to an electrical circuit as safety. May be problems with your gas-fire appliances of corrosion or loose wires resistance measurement shows a dead..