When your thermocouple is at fault, these are the top three reasons:
- Dirty thermocouple Over time your water heater will collect dirt, dust, and other types of debris. Buildup on your thermocouple can cause a malfunction. ...
- Bent thermocouple Your thermocouple easily bends and this could be the issue. ...
- Damaged thermocouple
What are the signs of a bad thermocouple?
- The probe/sheath design Choice of insulation materials Construction of thermocouple (grounded, ungrounded or exposed tip) Improper installation
- The wire or thermocouple junction itself
- The wires from the probe back to the electronics
- The electronics
How to tell if a thermocouple is bad?
MultiMeter Thermocouple Test Procedure
- First, remove the thermocouple.
- Secondly, turn on the meter and set it to Ohms. ...
- Thirdly, start the flame and put the tip of the thermocouple in the fire.
- Next, ensuring the tip is nice and hot from the flame, take one lead from the meter and put it on the shaft of the thermocouple and the other lead ...
How do I know if my thermopile is bad?
- 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.
- Remove the thermopile wiring connector from the gas control. ...
- Connect the red positive lead to the red thermopile wire, and the black lead to the white wire.
Why do my thermocouples keep going bad?
How do I make my pilot light higher?
- Locate the access plate on the front of your furnace, and unscrew the screws that are connecting the access plate to your furnace.
- Observe the flame.
- Turn that screw counter-clockwise, and the flame should grow.
- Rotate the screw on the pilot light clockwise, and the size of the flame will decrease.
How often should thermocouples be replaced?
Thermocouples can last up to 10 years if properly installed and maintained, while furnaces can last 15-20 years, although either may wear out sooner in multifamily units.
How do you fix a pilot light that keeps going out?
Dirty Thermocouple If it's filthy shut your gas off so that the unit can cool down, then gently clean it by carefully rubbing it with fine grain sandpaper. When you're done, simply turn the gas back on and light the pilot again. If dirt or grime was the issue, your light shouldn't go out again!
How do you troubleshoot a thermocouple?
1:473:21How to test a thermocouple with a meter (grounded & ungrounded)YouTubeStart of suggested clipEnd of suggested clipIf I take my wire and attach it to anywhere along the sheets of the probe. I attached to the sheathMoreIf I take my wire and attach it to anywhere along the sheets of the probe. I attached to the sheath and I'm getting continuity this is a grounded thermocouple if this was an ungrounded thermocouple.
Can you clean a thermocouple?
Yes, you can clean a thermocouple, but the task must be done with a light touch. Remove the thermocouple from the process assembly, using a steel wool or emery cloth, lightly clean the tip removing any build up. Cleaning a thermocouple is not a fix for an issue, such as inaccurate readings.
Why does my pilot light keep going out on my propane heater?
If the thermocouple is too far from the flame, this can cause the pilot to go out and shut down the propane heater; you can fix this easily by moving the thermocouple closer to the flame. The thermocouple could also be worn out, in which case it needs to be replaced.
Should thermocouple be in pilot flame?
The pilot flame should touch the thermocouple at a specific level. If the flame is blue and weak, and barely reaches the thermocouple, it needs to be stronger. If it extends well above the thermocouple, it's too strong.
Can I bypass a thermocouple?
Realistically, you have just disabled the thermocouple, but you can also reach in and unclip it from its holding bracket where it meets the pilot light. In most cases it will be held on with a gravity clip, but some are held on with a screw that must be removed with a small screwdriver.
Is the thermocouple supposed to be red hot?
When heat is applied to that hot junction, a small millivoltage is created. This develops because of temperature difference between the hot junction and what is called the cold junction. The flame has to envelop the upper 1/2" to 3/8" of the thermocouple and the tip should glow a "dull red".
Are thermocouples universal?
Universal Gas Thermocouple includes universal adapter fittings and is compatible with screw-in, push-in or clamp-type pilot burners. It is designed for gas furnaces and 30 mV systems. The element is built for reliability and long life.
Can a thermocouple be fixed?
If the pilot lights but the flame goes out as soon as you release the button after holding it for 60 seconds, then the thermocouple is bad. It's possible to replace the thermocouple without removing the burner assembly, and many repair people do this.
Why does my pilot light keep going out on my water heater?
Thermocouple Issues If it senses that your water heater pilot light keeps going out, the thermocouple will shift off the gas supply to the heater. Over time, thermocouples can malfunction, accumulate dust buildup, or the device can get bent away from the pilot light's flame.
Can I use sandpaper to clean a thermocouple?
In cleaning a thermocouple, you need some steel wool or 60-grit sandpaper, and a cloth. First, turn off the gas supply, unscrew the thermocouple and then clean it with steel wool or sandpaper then wipe down with a cloth to remove residue. I clean our thermocouple every six months to avoid getting it coated with soot.
How long does a thermocouple stay lit?
Thermocouple keeps burning out. Looking at 1 or 2 within 2 week period ! Tried different brands, the pilot will only stay lit for 3 minutes then automatically shuts down.
Can a thermocouple hold a gas valve open?
This is not necessarily a thermocouple or a gas valve problem, but possibly just a matter of cleaning or adjustment. Thermocouples generate an extremely weak current which can just barely hold the gas valve open under normal circumstances. If you recently replaced your thermocouple, odds are good there is a tiny bit of contamination between the new thermocouple contact and the port on the gas valve where it makes an electrical connection. The contact between these two needs to be very clean to work reliably.
How to tell if a thermocouple is failing?
Once you have located the thermocouple, do a visual inspection. You are looking for a few things. The first is signs of contamination on the tube , which can include discoloration, cracks, or pinholes.
How does a thermocouple respond to temperature?
The thermocouple responds to changes in temperature by producing an electrical current that causes the gas valve that supplies the pilot light to open when the temperature is high or to close when there is no direct heat source.
How to test a thermocouple?
Step 2: Open circuit test of the thermocouple 1 Before the test, turn off the gas supply because you must first remove the thermocouple. 2 Remove the thermocouple by unscrewing the copper lead and connection nut (first) and then the bracket nuts. 3 Next, take your meter and set it to ohms. Take the two leads from the meter and touch them—the meter should read zero. Once this check is done, turn the meter back to volts. 4 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. 5 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. 6 A working thermocouple will give a reading of between 25 and 30 millimeters. If the reading is less than 25 millimeters, it should be replaced.
What is a thermocouple made of?
The thermocouple is made up of a tube, a bracket, and wires. 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.
How many millimeters does a thermocouple read?
A working thermocouple will give a reading of between 25 and 30 millimeters. If the reading is less than 25 millimeters, it should be replaced.
How to inspect a furnace thermocouple?
How to Inspect Your Furnace’s Thermocouple. You will need a wrench, multi-meter, and a flame source, like a candle or a lighter, to perform the test.
Can you inspect before a HVAC test?
Be sure to inspect before you test, however, to ensure that there are no obvious problems that could affect the readings from testing! If you’re uncomfortable performing this test yourself, be sure to call a licensed HVAC contractor who can help you.
How Does a Pilot Thermocouple Work?
The thermocouple in a furnace pilot performs a safety role. It is installed such that it’s sensitive (the tip is equipped with a sensor) is dipped in the pilot flame when the pilot is lit. This way, the thermocouple helps the furnace keep track of the pilot flame and act appropriately if the gas goes out accidentally.
What Causes a Thermocouple to Go Out?
The thermocouple can go bad for many reasons. However, the three main reasons are metal fatigue, oxidation, and thermal shunting.
How to Install a Pilot Light Thermocouple
You need a screwdriver and a replacement thermocouple for this process. However, you can also use the old thermocouple if the multimeter test above shows that it still works. Here’s how to proceed;
FAQs
How Do I Reset my Thermocouple? To reset your thermocouple, locate the small reset button in the center of the switch and press it for 30-60 seconds to give the thermocouple time to heat up. Then release the button and watch to see if the pilot light goes out.
Summary
Now you know why your furnace pilot won’t stay lit even after replacing the thermocouple. You also know how to test a thermocouple and re-install an incorrectly installed thermocouple. Don’t hesitate to call the experts if the problem persists.
Why is a thermocouple erroneous?
Because a thermocouple measures temperature differentials, any temperature fluctuations around the reference junction (cold junction), which has the known temperature, result in an erroneous temperature reading. Solution: Make sure no fans or other sources of cooling or heating are located near the reference junction.
Why is my thermocouple measuring error?
The following are the six most common causes of thermocouple measuring errors, followed by ways to rectify them: 1. Selecting the Wrong Type of Thermocouple on the Transmitter. You can run into problems if you choose the wrong type of thermocouple when inputting the settings into the transmitter during installation.
How does a thermocouple work?
A thermocouple works by taking the difference in voltage between the two junctions, explained by the Seebeck effect. The measured voltage is converted into a temperature unit, with the temperature reading displayed on a device or transmitted to a remote location. Although thermocouples are reliable, temperature measurement errors can occur ...
Why are thermocouples used in industrial applications?
Thermocouples are among the most popular temperature measurement instruments in industrial applications because of their versatility and ease of use. However, measurement errors can occur. This article discusses the six most common causes of thermocouple errors. Thermocouples are robust temperature measurement devices that are accurate enough ...
What is the temperature range of a thermocouple?
Relatively inexpensive compared to other temperature measurement technologies, thermocouples are valued for their ability to measure a wide temperature range: from –200° to +1250°C (–328° to +2282°F).
What happens if you reverse the polarity of a thermocouple?
If you accidentally reverse the polarity of the thermocouple lead wires, the measured temperature will be incorrect by the difference in temperature of the two ends of the leads. The problem is understandable because red is the usual color for positive charges, whereas the red wire in thermocouple cables typically contains the negative signal.
Do thermocouples have to be color coded?
Solution: Almost all thermocouples are color coded by type, so you usually just need to confirm the color of the thermocouple jacket and match the settings on the transmitter. 2. Problems Related to the Thermocouple Extension Wire.
What happens if the pilot light goes out on a water heater?
If it senses that your water heater’s pilot light has gone out, the thermocouple will shift off the gas supply to the heater. Over time, thermocouples can malfunction, accumulate dust buildup, or the device can get bent away from the pilot light’s flame.
Why won't my water heater pilot light stay lit?
Another reason your gas water heater pilot light won’t stay lit could be due to not having enough combustible air. Your water heater requires air to keep the pilot light burning. Otherwise, the flame goes out. Ensure that the water heater is not surrounded by clutter, lint, or debris to increase the amount of combustible air.
What to do if your water heater pilot light won't work?
Our certified technicians are available 24/7 to come out, take a look, and recommend the best way to get your water heater working safely and efficiently.
Can you replace a thermocouple?
Yes. If you are DIY-inclined you may be able to replace the thermocouple yourself. To do so it’s easiest to shut off the gas valve and remove the whole burner and thermocouple assembly. Though if you have no clue how to do small repairs, it’s better and safer to call someone who does.
How to fix a broken thermocouple?
The solution: First, cut off the gas supply, switch off your heater, and wait for the thermocouple to cool off. You’ll have to manually bend or straighten the thermocouple back to position. It needs to be close enough to the pilot light that it slightly touches or wraps around the blue flame. 4. A Broken Thermocouple.
What is the purpose of a dirty thermocouple?
2. A Dirty Thermocouple. The thermocouple is the brain of your water heater. It’s responsible for closing the gas valve when it senses the pilot light is off. The thermocouple is triggered by an electric current produced by the pilot light. It acts as a safety device to prevent gas leaks.
Why does my pilot light go out?
The flame will go out if the tube is clogged with dirt or debris. Sometimes, the tube might be partially clogged and supplying very little gas for combustion- No wonder your pilot light keeps going out. The Solution: Thorough cleaning should do the trick. Use a slender needle to gently unclog the tube.
Why does my water heater pilot light go out?
It acts as a safety device to prevent gas leaks. Therefore, a dirty thermocouple might be the reason why your water pilot keeps going out. A layer of dirt and grime can hinder the electric current from reaching the thermocouple. As a result, the gas supply will be cut off and the pilot light will go out.
Why does my water heater flame out?
Don’t worry, there is nothing wrong with your heater. It’s just dirt build-up. The Pilot tube supplies gas to the pilot light for combustion. The flame will go out if the tube is clogged with dirt or debris.
What happens if the thermocouple is less than 20 volts?
If the voltage supplied by your thermocouple is way less than 20MV, then the device is surely broken and needs to be replaced. The Solution: You can move the thermocouple close to the pilot light if the multimeter reading is close to, but not at 20MV.
How to tell if water heater is faulty?
The first sign of a faulty electrical system is if your water heater suddenly shuts down. The Solution: Immediately switch off your water heater and call a technician.
Why Does My Gas Fireplace Keep Going Out?
If you’re struggling with keeping your fireplace lit after 20 minutes to an hour, chances are that you have a sensor or a valve that’s going bad.
How the Pilot Works in Your Gas Fire
Starting up a gas fireplace begins with shifting the pilot light to the “on” position. In some cases, you may need to hold it longer to allow the fire to “kick on.” When you first attempt to start up the fire, you should always keep an eye on the pilot light.
How the Thermocouple Works
The thermocouple must stay in constant contact with the flame of the pilot. It is essentially a sensor that measures temperature and is made up of two different types of metals, joined on one end.
How the Oxypilot Works
The oxypilot is another sensor that is designed to put out a gas fire when there is not enough oxygen in a room. It is a safety mechanism that protects you and your family from carbon monoxide poisoning.
How To Troubleshoot (And Fix) Your Gas Fireplace
A gas fireplace that keeps shutting off is annoying, but it’s not the end of the world. The gas fireplace issues that you’re dealing with are usually fairly fixable. Here’s how to make your gas fireplace work again:
When Should You Call A Professional?
If you are working with a gas fireplace and can’t seem to fix the problem through regular cleaning or troubleshooting, you should call a professional. Due to the risk of fire hazards and the difficulty that can arise when it comes to finding the right parts, most experts agree that it’s better to call a licensed and certified gas technician.
Related Questions
For most thermocouple issues, gentle cleaning with a fine-grit sheet of sandpaper or a Magic Eraser will fix your thermocouple. In most cases, a thermocouple that has gone bad won’t be able to be fixed. Thankfully, it’s fairly easy to replace a thermocouple and it’s not that expensive to do.
