Commercial Oven Problems: Malfunctioning Thermocouple

Thermocouple is a safety feature in commercial gas ovens and many other gas appliances. If it goes bad, the pilot light of your commercial oven won’t work. You can consult a commercial oven repair technician to determine if the thermocouple is faulty or keep reading to learn the common signs of a malfunctioning thermocouple and how to test it.

Signs Of A Malfunctioning Thermocouple

The Pilot Light Won’t Stay Lit

If a commercial oven pilot light is not lighting at all, it isn’t due to the thermocouple. Many people consider it the fault of a thermocouple if their commercial oven is lighting. A thermocouple is not responsible for lighting the pilot light. It’s responsible for keeping the pilot light lit on your oven.

Therefore, if the pilot light of the oven is lighting and you can see the flame, but it turns off after that, the thermocouple is to blame.

On the other hand, if the pilot light is not igniting or not producing a flame, there can be an obstruction in the pilot tube or the gas supply is turned off. Clean the pilot tube and other components.

Furthermore, when you can turn on the pilot light, but the flame has a different color than blue or it appears small, the commercial oven won’t work and the cause isn’t a malfunctioning thermocouple. An obstruction in the pilot tube usually reduces the gas flow and makes the flame appear small. Due to the smaller flame, the thermocouple doesn’t heat up enough to each a high temperature that would open the gas valve. In turn, the oven won’t heat up.

The Tube Is Discolored Or Has Holes In It

To determine if the thermocouple is malfunctioning, you should observe its appearance. If you notice discoloration, cracks, or small holes in it, you should replace it.

Worn Or Corroded Wiring

When checking out the condition of the oven thermocouple, make sure the wiring doesn’t have bare spots or missing insulation. If you find some parts with bare wires and no insulation, the thermocouple is faulty.

How To Test A Thermocouple Of A Commercial Oven

You will have to remove the thermocouple for the test. If you can’t, consult a professional.

  • Remove the thermocouple from the oven. Unscrew the copper lead and the nut. After this, unscrew the bracket nuts. Make sure you turn off the gas supply to the oven before taking the thermocouple out.
  • Take a multimeter. It’s preferred to use the one with red and black clamps.
  • You’ll be testing the multimeter first, so set it to ohms by spinning the dial on the multimeter to the correct symbol. Touch its two leads together and check the reading. It should be 0. After this process, switch it back to volts.
  • Use a lighter or any other thing for lighting a flame. Keep the tip of the thermocouple in the flame and allow it to become hot.
  • When the thermocouple is hot enough, take one lead of the multimeter and attach it to the two sides of the thermocouple.
  • Check the reading on the multimeter. If the reading is between 25-30 mv, the thermocouple is fine. But if the reading is lower than 25mv, it means that the thermocouple can’t keep the pilot light on and you must replace it.

Choosing A Thermocouple

You won’t have difficulty in getting a thermocouple for your commercial oven and they don’t have any vastly different types. Bear in mind that thermocouples are attached to a safety valve. Some thermocouples come with safety valves. So, check out which thermocouple you have.

The Pilot Light Doesn’t Stay Lit After Thermocouple Replacement

If you detected the problem and replaced the thermocouple correctly, the pilot light will stay lit in your commercial oven after the replacement of the thermocouple. If the pilot light is going out even after the replacement, the issue may be with the safety valve. Therefore, it’s better to replace both components together to save time or get the oven inspected by an expert before replacing a component.


If the thermocouple of your commercial oven is defective, the pilot light will turn off quickly after lighting. Look for the signs of a faulty thermocouple and replace the component so you can carry on using the appliance and serving your customers. For quick inspection and replacements of oven components, call in a commercial appliances repair service. topac

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