Gas Hob Burner Not Staying Lit | How To Test Hob & Oven With Thermocouple?

Gas Stove Top Hob Burner Not Staying Lit Repair Guide

If you're having trouble with your gas oven or hob, where the flame ignites but goes out as soon as you release the knob, this guide will help you understand the problem and show you how to test for it. Normally, when you push and hold the knob down, the flame lights up and after a few seconds, you can let go of the knob and the flame continues to burn. This guide explains the mechanism behind this and how to test it.

We would recommend you watch our video since we're showing related components and possible problems about gas hobs and cooker hobs.

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Understanding the Gas Valve and Thermocouple

The gas valve and thermocouple are key components in this process. The thermocouple, invented in the 1800s by Thomas C. Beck, produces a small amount of DC millivolts. This energy travels to a valve inside the gas valve. When you press down the knob, you're bypassing the electronic valve, giving the thermocouple enough time to heat up. When you release the knob, the valve should remain open as long as the thermocouple continues to supply DC millivolts.

In a faulty system, when you press the plunger or valve down, the valve does not lock in place because no thermal energy is being produced. However, when heat is applied and the valve is pressed down, it locks in place. Once the heat source is removed, the valve will unlock and shut down after a preset time, making your gas appliance safe.

How to Test Gas Hob Thermocouple?

Testing a thermocouple for its energy production is straightforward. Set your meter to measure millivolts of DC electricity. Connect the positive lead to the outer rim and the negative lead to the inner rim of the thermocouple. Position the thermocouple in a flame. As the flame heats the thermocouple, it produces energy according to the Seebeck effect.

For single wire thermocouples, they function similarly to the twin wire version. The only difference is that the single wire version uses the appliance's chassis to conduct the electrical energy. Over time, corrosion can occur, leading to a bad connection and inaccurate readings sent to the valve.

Once heat is applied to the thermocouple, you can expect to see between 10 and 50 millivolts DC, depending on the thermocouple's construction and the metals used in its manufacturing. Once the flame is extinguished, the voltage dissipates quickly. Once the energy level drops below the threshold needed to keep the valve open, the valve will shut.

If you determine that your thermocouple or thermo-electric device needs replacement, be sure to have your appliance's full model number to ensure you get the right part. This applies to all components like spark igniters, jets, and gas valves.

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