How often do thermocouples need to be replaced?

Author: Osbaldo Stanton  |  Last update: Monday, June 2, 2025

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.

What is the life expectancy of a thermocouple?

* Standard Thermocouples: Typically last 1-3 years in industrial applications. * Specialized Thermocouples: Can last 5-10 years or longer in controlled environments. * Different thermocouple types (e.g., Type K, J, T, or R) have varying durability based on their materials and intended applications.

What are the signs of a bad thermocouple?

For a bad thermocouple, you will normally see a high temp displayed, and the controller will immediately go into cool down mode. You are showing heat up mode, and erratic temperature displays.

How do I know if my thermocouple needs replacing?

The best way to verify that you need a new thermocouple is to see if your pilot light is lit. If the pilot light can't hold ignition, that means either a problem with the gas supply or, more likely, the need for thermocouple replacement.

How much should a plumber charge to replace a thermocouple?

If your thermocouple goes bad, there is only one thing to do: Replace it. If you hire a professional plumber to do this, it may cost up to $200 for the labor.

HVAC: What Is A THERMOCOUPLE & How Does It Work? (Basic Working Principal) How It Works

Can I replace a thermocouple myself?

Replacing a thermocouple is a relatively easy fix that can take less than two hours. 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.

What causes thermocouples to go bad?

Overheating: Each thermocouple is designed to operate within a certain temperature range. Operating beyond this range can damage the thermocouple's materials, causing them to degrade faster than normal. Contamination: Exposure to harmful chemicals or debris can affect the thermocouple's performance.

Will the pilot light go out if the thermocouple is bad?

The thermocouple is a safety device designed to shut off the gas valve if the pilot light goes out. Although, if your thermocouple is old, worn, damaged, wrongly positioned, or malfunctioning, it could have wrongly shut off the gas valve and prevented your pilot light from staying lit.

What is the common problem in thermocouples?

Temperature sensor and thermocouple errors can be caused by various factors, such as mechanical damage due to physical stress, abrasion, or corrosion; electrical interference from nearby sources of electromagnetic radiation; wiring problems like loose, broken, or mismatched connections; calibration issues that cause ...

Should I clean or replace thermocouple?

Can I clean my thermocouple instead of replacing it? If the thermocouple tip is only lightly corroded or covered in dust/debris, cleaning may restore functionality. But if you find any cracks, bent wires, or significant corrosion pitting on inspection, replacement is the safest option.

How do you check thermocouple health?

Disconnect it from the gas valve and connect a multimeter set to millivolts. Apply heat to the tip and check the reading. A properly functioning thermocouple will generate 15-35 millivolts when heated. If below 15 millivolts, the thermocouple must be replaced.

How much does a thermocouple cost?

Furnace Thermocouple Replacement Cost

If you're comfortable handling small furnace repairs, you can purchase a furnace thermocouple for about $10 to $20 from a hardware store or online. Replacing the thermocouple requires some basic tools and familiarity with the furnace's inner components.

Is there a way to 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.

Do thermocouples degrade over time?

With an operating temperature range of −40 to 2,300°F (−40 to 1,260°C), all Type K thermocouples will experience aging and drift over time.

Can thermocouples fail intermittently?

Sometimes sensors can break or degrade in harsh environments. You might be suffering from intermittent thermocouple failure or instruments might be showing “Open Circuit”.

What stops a thermocouple from working?

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.

How do I know if my thermocouple is bad?

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 goes bad in a thermocouple?

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 reliable are thermocouples?

Generally, thermocouples can measure temperatures with an accuracy of ±1°C to ±2°C.

Is a thermocouple hard to replace?

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.

Why won't my brand new thermocouple stay lit?

Once you have replaced the thermocouple, turn on the furnace and check to see if the pilot light stays lit. If your pilot light doesn't stay lit, it may be due to something blocking the thermocouple. You can try cleaning or replacing it, but if that doesn't work, you may need to call a professional.

How to test a thermocouple?

Thermocouple Check Put one alligator clip on copper wire of thermocouple and the other clip on silver tip at the end of thermocouple. Ignite pilot to get readings. Readings should be approximately 20 mv. Continuity Check (making sure switches and wiring are OK) Turn multimeter to the continuity sign.

What does a dirty thermocouple look like?

To figure out if your thermocouple is dirty, look at its tip. If you notice the tip is covered with a layer of soot, this means it needs to be cleaned as soon as possible. If you ignore this, you'll start having problems with the pilot light staying lit on a consistent basis.

How often should thermocouples be calibrated?

How often should a thermocouple be calibrated? We recommend that thermocouples are calibrated once every 12 months to ensure they maintain accurate, repeatable and high-quality temperature measurements.

Why won't the pilot light stay lit?

Common reasons include a nearby draft, dirt buildup, or a malfunctioning thermocouple. Another pilot light drawback is energy waste. Since the pilot light needs to remain active, your furnace is always consuming some gas. It's not a lot—usually just a few therms of gas a month–but that obviously adds up over time.

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