What causes thermocouples to go bad?

The presence of oxygen causes a reaction in the thermocouple that can wear down the part and make the wires become thinner and more brittle. Oxidation can be caused by a small amount of oxygen making its way into a sealed environment and reacting with the pure metal of the thermocouple.

How long should a thermocouple last on a water heater?

How Long Should a Water Heater Thermocouple Last? If properly installed and maintained, thermocouples can last for up to 10 years. Gas water heaters, in their turn, have a general lifespan between 8 and 12 years, so if you manage to take great care of your unit, you might not have to replace the thermocouple at all.

How much does it cost to replace thermocouple?

1 cause of pilot lights that won’t stay lit is a worn-out thermocouple. It’s easy to replace and a new one costs $5 to $10. Rather than trying to unfasten the thermocouple inside the water heater’s burning chamber, it’s easier to remove the whole burner and thermocouple assembly.

How do you know when to replace thermocouple?

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.

Do thermocouples degrade over time?

Aging and Drift in Type K Thermocouples. With repeated exposure to high temperatures, a type K thermocouple becomes less accurate. Aging is a phenomenon that results in higher-than-accurate temperature readings, while drift results in lower-than-accurate readings.

How often do thermocouples go bad?

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.

Can thermocouple be cleaned?

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.

What happens if a thermocouple fails?

When a thermocouple fails, the pilot light won’t stay lighted. A burned out or broken thermocouple should be replaced.

How do you tell if the thermocouple is bad on a water heater?

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.

How do I clean a thermocouple?

The best way to clean your thermocouple is to use either a piece of steel wool or the coarse side of a sponge to gently clean off any soot or other remnants. You can use a pencil eraser to clean between the threads of the screw that connects the thermocouple to the control valve of your system.

What would cause a pilot light to keep going out?

A faulty, misaligned, dirty, or damaged thermocouple is often the culprit behind your pilot light going out. The thermocouple is an automatic safety shutoff device that prevents the gas valve from opening if the pilot light is out.

What would cause a pilot light to not stay lit?

The Buildup of Dirt or Debris Around The Pilot Light – Over the years it’s easy for dust, debris, and dirt to build up on the inside of the intake valve where the pilot light resides. This makes it difficult for the flame to breath and as a result causes the pilot light to go out suddenly.

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.

How much does it cost to replace a thermocouple on a furnace?

Replacing a thermocouple costs $150 to $250, mostly due to labor time. On older models without an ignitor, it checks to make sure your pilot light is lit. If it’s not, it’ll shut the gas off.

Are thermocouples universal?

Universal thermocouples come in lengths from 15 to 36 inches. An 18 or 24 inch will suffice for all residential water heaters using universal kits. Almost all older waters heaters and many of the newer style units with a sealed burner compartment and a viewing window will use this thermocouple.

What is the most common thermocouple failure mode?

The most common failure mode for thermocouples is for them to fail open, this is known as thermocouple burnout. Burnout can result from a variety of reasons including the thermocouple experiencing a temperature in excess of that for which it was designed, metal fatigue, and oxidation.

Do thermocouples drift over time?

Thermocouple drift is the potential for thermocouples to lose accuracy over time, moving in a positive direction. Thermocouple drift is more common when a thermocouple has been operating at higher temperatures for a prolonged period.

Can a thermocouple fail high?

There are any number of ways a thermocouple can fail. It can short out, the sheath can fail, it can be damaged during operation or installation, it can be improperly installed, etc. The key is to perform a thorough root-cause analysis and prevent the failure again in the future, if possible.

How do you fix a bad thermocouple?

Furnace – Thermocouple | Repair and Replace

Why won’t my pilot light stay lit in my gas fireplace?

If the pilot light on your gas fireplace won’t stay lit, a very likely culprit is a component called a thermocouple. A thermocouple is a safety device and is a component of the ignition system. Its purpose is to not allow the gas valve to open if the pilot light isn’t lit.

How do you check a thermocouple?

How to test a thermocouple with a meter (grounded & ungrounded)

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.

How do you adjust a thermocouple?

Adjusting the Thermocouple

Correcting the first condition is a simple process. Simply shut off the gas, reach under the burner and push or pull the probe to reposition it. If the thermocouple is faulty, remove it by unscrewing it from the burner and pulling it out. Reverse the procedure to install a new one.