Once you've located the thermocouple, do a visual inspection. You're looking for a few things. The first is signs of contamination on the tube, which can include discoloration, cracks, or pinholes. Next, check the wiring for any signs of wear or corrosion like missing insulation or bare wire.
Cleaning the thermocouple
You can use Emery cloth sandpaper to gently clean any debris or build-up from the end of the thermocouple. If present, you should also clean off any corrosion where the power wire connects to the thermocouple terminal.
Over time, dirt and debris can build up on the thermocouple, preventing it from working correctly. To clean it, remove it from the furnace and use a wire brush to remove any buildup. You can also try using a small amount of sandpaper to sand away any rust lightly.
If the pilot flame ignites but goes out after you release the gas control knob, the cause may be a dirty or defective thermocouple. If the gas is on but the flame will not ignite at all, a pilot tube obstruction is the most likely issue. Remove the pilot tube from the gas valve and spray compressed air to clear it.
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.
Cleaning the thermocouple is a straightforward task that can restore its functionality and ensure your water heater operates efficiently. Regular maintenance helps prevent issues like pilot light failure and inconsistent heating.
The most accurate thermocouple calibration is achieved is by using a Fixed Point cell where the thermocouple's output is measured against a number of fixed points along the International Temperature Scale developed in 1990 ITS-90 at the fixed point transition of various metals along the scale.
(See Figure 2) Using a 7/16” wrench disconnect the thermocouple (left-hand thread) and pilot tube (right-hand thread). Using a 3/4” wrench disconnect the mani- fold tube (right-hand thread).
Can I use an alcohol wipe to clean off old CPU thermal paste? The short answer is, “Yes” — you can use an alcohol swab to clean up the thermal paste.
Symptoms Pilot won't light. Pilot lights but burner won't. System lights, but goes out after a while.
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.
To determine if your thermocouple only needs a good cleaning or requires replacement, it will come down to how often your pilot light is going out. If you're experiencing pilot light outages every few days or have a water heater that is over 10 years old, you'll do better by replacing the thermocouple.
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.
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.
To determine your system accuracy when you have a separate meter and probe, add the tolerance of the meter to the tolerance of the probe. The diagram at right shows the accuracy versus temperature for a typical thermocouple meter and probe.
A thermocouple is a sensor that measures temperature. It consists of two different types of metals, joined together at one end. When the junction of the two metals is heated or cooled, a voltage is created that can be correlated back to the temperature.
There's really just one telltale sign of letting you know when the thermocouple isn't working, and that's when the pilot light won't stay lit. If you experience this problem, it's important to have your thermocouple assessed as soon as possible.
Common Causes of Thermocouple Failure
Damage to the protective sheathing or the wire itself can result in inaccurate readings or complete failure. Overheating: Each thermocouple is designed to operate within a certain temperature range.
The Pilot Lights But Won't Stay Lit
If the flame lights and goes out when you release the gas control knob after holding it in for the recommended 20 to 30 seconds, that's the sign of a thermocouple malfunction.
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 ...
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.