The following are the six most common causes of thermocouple measuring errors, followed by ways to rectify them: 1. A burned out or broken thermocouple should be replaced. If the furnace still doesn't stay lit after cleaning, then its best to install a new thermocouple.Watch more furnace repairs: https://www.youtube.com/playlist?list=PLCo9SMjkdWBwU5dJaopTR09W7U05fEOF5___________________________00:00 Intro00:28 How it Works01:11 What You'll Need01:21 Identify the Thermocouple01:56 Cleaning03:16 Relighting04:13 Thermocouple Replacement___________________________AMRE Supply provides homeowners, service contractors, and property management with the parts and knowledge needed to get the best performance out of any property. Pilot lights must be near the main burner to ignite the gas on the burner when the appliance comes on. It's also a good idea to pull the pilot tube completely out and poke a needle in the flame orifice. If you have a gas water heater, gas wall heater or any other appliance with a gas burner that needs to cycle on and off, there's a thermocouple in your life. Finally, put back the thermocouple inside the box. Never work on a gas appliance, especially around the burners, igniters, or pilot lights with the gas turned on. But, how do you know if you have a bad thermocouple? Step 2: Hold a lighted match to the pilot orifice and turn the gas valve to the ON position. Don't try to adjust the mechanism or tamper with the gas line. Using a small pair of needle-nose pliers is a safe way to adjust the thermocouple clamp. Measure the resistance from pin to pin on the plug. Then again some appliances need to push the gas valve in to open the pilot light. For the actual test, turn on your flame source, and place the tip of the thermocouple into the flame, leaving it there until it is quite hot. Here I repair a thermocouple for my DT304 digital temperature logger using a home made small wire welder.The small wire welder is a work in progress. Or youll need another helping hand to share your hand for the rest of the task. 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. Turn the gas valve on the appliance to the Light Pilot setting. It is usually found near the system's pilot lights or burners. While checking the tip temperature of the fine tip while soldering an SOIC-8 part, the meter just up and quit measuring temperatures. If youve been measuring the temperature of soldering iron tips like I was, you should also check and see if a splatter of solder is shorting the thermocouple. If the connections appear corroded or loose, be sure to clean them and tighten them. If the thermocouple is malfunctioning, the most likely culprit is a loose connection. Be sure to turn off the power to the device before attempting to remove the thermocouple. That was odd. Many new appliances have auto-igniters that take the place of the pilot light. Sometimes youll notice tour appliances arent lighting or lighting sporadically. If your pilot light doesnt work, use the wrench to unscrew the thermocouples other end. There are all sorts of methods out there. Often the thermocouple connection points are overlooked, but are critical for proper readings. Be sure to inspect before you test, however, to ensure that there are no obvious problems that could affect the readings from testing! This article was co-authored by Gevorg Grigorian. Turn the appliance off. If the thermocouple wiring is bare, missing insulation and is touch together anywhere between the sensing - probe end, and the connection points, the thermocouple will read at the area where the bare wiring is touching together. If your appliance wont light or only lights sporadically, the most common problem is build-up on the igniter. How to Remove the Thermocouple in a Heat & Glo Fireplace, Omega: Thermocouple: Different Types, What It Is, and How to Replace One, High Performance HVAC: How to Test a Thermocouple with a Multi-Meter. Ive seen quite a few appliances require turning and holding the valve to control. For that, turn on the gas valve and put it in the Light Pilot setting. 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. Most appliances hold the thermocouples in place with a spring clamp. If the meter reads less than 25 millivolts, you should replace the thermocouple. Step 2: Under the mounting bracket at the thermocouple tube, unscrew the bracket nut that holds the tube in place. Your igniter may or may not have a pilot hole. Learn about the Maintenance and Handling of Thermocouples, Email: 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. Do You Need to Hire an Electrician? Before starting the job you must turn off the appliance. It will secure your own safety. link to Natural Ways To Keep Mosquitoes From Biting. First, inspect the flame. 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. If you can't get the flame to light at all, and you're sure the gas is on, there's probably an obstruction in the pilot tube. Unscrew the thermocouple from the gas valve and have a helper hold the gas control knob to keep the pilot burning. 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. A burned out or broken thermocouple should be replaced. Compatible Thermocouple Calibration Type? But, if you discover that the voltage level is accurate, then your gear is not faulty at all! 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. If the connections appear loose or corroded, then you will need to clean them and tighten them. You should also turn the appliance off before working around the pilot light and burner. If the reading is less than 25 millivolts, the thermocouple is bad and needs to be replaced. By creating an account you agree to the Hunker, How to Change a Thermocouple on a Fireplace, How to Troubleshoot an Electronic Ignition for a Superior Gas Fireplace, Adjusting the Gas-to-Air Ratio on a Heat-N-Glow Fireplace. [8] The tube connects to the gas valve below the pilot light. What should I do if my thermocouple is coated with a white powder? Appliance Repair Expert. Your email address will not be published. Set your voltage meter to read voltage (V) in millivolts. When a thermocouple fails in your control system, bad things happen. Generally, thermocouples have no wire connections. It does this by sending a tiny electric current to a sensor on the gas valve signaling the valve to stay open. THERMOCOUPLE FUNDAMENTALS Service Life The igniter is usually immediately adjacent to or at the edge of the burner. The auto-igniter then creates an electric arc to the burner, igniting the gas. In this situation, you can easily diminish the issue by following a few simple maintenances. So that it can produce an ample amount of electrical flow. An aged heater can create issues with gas valves, control panels, or even burners. In our final section, we will conclude our discussion of repairing major appliances with a detailed examination of -- of course -- motors. If you have gas-fired appliances such as a water heater, space heater, or cookstove, these appliances may have one or more thermocouples. I know this is the first question that hits your mind. To do this, youll need a voltmeter with a thermocouple probe. Just using the probe had twisted the wires around inside the strain relief and shorted them. This is what a cheap K-type thermocouple looks like: Note that the wires to the thermocouple (the little metal ball at the end of the cable there in the upper left corner of the picture) are bare - they can easily be shorted by bending or twisting the wires. How Does a Gas Water Heater Thermocouple Work? "Very clear and simple drawings make it easy to learn the basics in a short time. Richmond Water Heater Thermocouple Replacement: The How-To Steps 01. Connection from the thermocouple to the valve. 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 . In this task, youll need to heat the thermocouple. Just the fact that you have to shut down and replace a thermocouple means lost revenue. A thermocouple is a device that produces a small electric current when it is heated. The thermocouple has two dissimilar metals that form an electrical circuit. A functioning thermocouple should also show a few millivolts DC when hot. To gain access to the pilot burner, pull the door out of the furnace housing. If all heater zones show continuity then check the resistance of each zone and compare it to the value shown on your hot-runner. 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. Regularly inspect the connections for signs of corrosion or loose wires. It may have gotten crushed or one of the wires may have broken off. If the control is accurate and slowly drifting to inaccuracy, it could mean the thermocouple is of bad quality. Remember that you are working around open flames. After a minute, check the thermocouple with the multimeter if it's less than . Some thermocouples will look slightly different, so check your furnace manual. Look around the igniter as well and make sure there is no build-up on the burner or near the igniter. Gevorg holds a BS in Business Administration and Management from California State University-Northridge. Now that is working again, it shows about 15 ohms. Multiple connections should be avoided in order to improve accuracy. The tube connects to the gas valve below the pilot light. Replacing a thermocouple is a relatively easy fix that can take less than two hours. The only way for that to be possible (lower resistance at the plug than at the thermocouple) was for there to be a short in the wiring in the plug. Take off the valve housing aside through a 133mm socket wrench. Cleaning a thermocouple is not a fix for an issue, such as inaccurate readings. Thermocouples are designed to detect a pilot light's loss of heat and close the gas valve to prevent a gas leak. {"smallUrl":"https:\/\/www.wikihow.com\/images\/thumb\/0\/04\/Test-a-Thermocouple-Step-1.jpg\/v4-460px-Test-a-Thermocouple-Step-1.jpg","bigUrl":"\/images\/thumb\/0\/04\/Test-a-Thermocouple-Step-1.jpg\/aid9649384-v4-728px-Test-a-Thermocouple-Step-1.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"