How Does a Thermocouple Work on a Patio Heater?

A thermocouple is essentially a safety device. When two wires are connected, a spark occurs, which can be different depending on temperature changes. This change is detected by a sensor and if it is too different from the norm, then the thermocouple will shut the heater off.

If you have a patio heater, you may at some point have wondered how it works. If you have, then the article below will explain all about the heater on your patio.

That is the basic idea behind a thermocouple, but for a more detailed description, as well as a guide for you to learn all you need about thermocouples to keep them working correctly.

close up of thermocouple for patio heater

Related Reading: How To Clean A Thermocouple On A Patio Heater [QUICK GUIDE]

How Does a Thermocouple Scientifically Work?

Thermocouples work via what we call the thermoelectric effect. This means that thermal energy is converted to electrical energy in the process. The wire conductors are made of two separate metals, and when they are connected, a voltage occurs.

The fact that these wires are two different metals means that the voltage can change with different temperatures, due to the variation of electron density of the different metals. When these temperature changes are detected, the voltage is calculated by the sensor.

Generally, the wires are made from cheap and common metals such as:

  • Copper
  • Iron
  • Nickel

How To Know If The Thermocouple Is Malfunctioning

If your patio heater isn’t working correctly, then there is a chance that the thermocouple might be the issue. To know if you might need to bypass or even replace a thermocouple, then there might be a few signs to keep an eye out for:

  • Missing insulation or exposed wires can show some wear or corrosion on the wiring
  • Any damage on the connectors
  • Discoloration, cracks and other damage on the tube could be signs of tube contamination

Where Is The Thermocouple In The Patio Heater?

If you need to troubleshoot, replace or bypass it to fix your heater, you’ll need to know where it is.

If you’re not sure where the thermocouple is, then start by looking around the flame. The thermocouple usually has a few typical components:

  • A tube
  • Wires
  • Copper casings
  • A bracket

Usually, copper wires connect the gas valve from under the bracket, with the bracket are held together by a nut. They may look different depending on each heater, so make sure you check to make sure that you know where it might be.

How to Test the Thermocouples

If you think that you would like to test your thermocouple, then it is recommended to hire a professional. But if you would like to perform the test yourself, then you will need a few items to perform the test:

  • A wrench
  • A multimeter
  • Something to spark a flame, like a candle, match or lighter

To perform the test, you will need to follow these instructions:

  • Turn off the gas before starting
  • Unscrew the connection nuts on the brackets and undo the copper wires to remove the thermocouple
  • Set your meter to ohms. This means that when you touch the meter’s leads together, it should be reading zero. Return the meter to volts if you don’t.
  • Turn on the flame source
  • Place the thermocouple in the flame and make it heat up until it is to a significant temperature
  • Connect the multimeter’s leads to the thermocouple. It should have one lead on one side, and the other lead should be at the end of the previous one by the flame.
  • If the reading is between 25 and 30 mm, then that means that your thermocouple is working correctly. If it is less than 25 millimeters, you might need to either bypass or replace your thermocouple.

How To Bypass a Thermocouple

It would be recommended that if you discover that your thermocouple isn’t working correctly then you replace it, but that can be expensive. If you don’t have the funds for that, then you might be able to bypass the thermocouple to try and extend it until the time where you can replace it.

To be able to bypass a thermocouple, you will need the following things:

  • Pliers
  • 8mm wrench
  • 13mm socket wrench

In order to bypass the thermocouple, you need to follow these instructions:

  • First, remove the spring valve from the inside the thermocouple. To do this, move the switch wire out of the way and use the 8mm wrench to take out the thermocouple.
  • Pull the valve housing out of your way with the 13mm socket wrench
  • Remove the valve with the pliers.
  • Once you have taken out the spring valve, put the thermocouple back

After you have done all of this, the gas should flow directly into the burner when it is turned on, and the thermocouple should be bypassed. It is recommended that you replace it as soon as possible though, as it is a safety measure and it can be dangerous to be without it for any length of time.

How to Replace Thermocouple on Outdoor Patio Heater

When you have the budget for a new thermocouple, then you will need the following equipment:

  • A screwdriver
  • Pliers
  • 8mm wrench

These should be enough to allow you to remove and install the new thermocouple.

Removing The Broken Thermocouple

The assembly of the ignition should be held by one screw and should be able to be undone by a screwdriver.

  • Remove the covering on the front of the heater
  • Unscrew the box housing at the back of the thermocouple and move it out of your way
  • Unscrew the nut that holds the thermocouple with the pliers.
  • You should be able to pull the wire connectors loose without any other equipment

Putting In The New Thermocouple

  • Connect the connectors of the new thermocouple to the tilt switch
  • Connect the other end to the gas valve
  • Tighten the connections with the 8mm wrench
  • Put the wires back through the thermocouple and box housing
  • Put the covering back on the front of the heater

In short, you take it out using one process and reverse this process to put it back. It is recommended that you get a professional to do this task for you, but if you insist on doing it yourself, then switch off the gas and electricity and make sure you research what you’re doing and what model of heater you have before you start.

How To Clean The Thermocouple

If the thermocouple gets covered in dirt, then it might have some trouble lighting up, therefore, cleaning it is an easy way to ensure a long life.

  • First, turn off the gas
  • Unscrew the bolts of the thermocouple and remove it
  • Use a damp rag and no chemical cleaners, and give the inside a wipe down
  • Afterwards, use a dry towel to pat it down
  • Rinse the inside of the tube with the hose
  • To ensure it is dry enough, let it air dry
  • Reattach the thermocouple only after it is completely dry
  • Reconnect the gas
  • You may have to tighten the connection between the gas valve and the pilot


Overall, the thermocouple is a safety measure that is built into many patio heaters, and it works by a thermoelectric process. It has two wires made out of different metals and the voltage it produces is calculated by the sensor and tells the heater whether to keep the light on.

If it malfunctions, then the heater may not work. You might be able to bypass or replace it yourself if this happens, however.

Continue Reading: Common Patio Heater Problems & Fixes