Thermocouple Burn Out

The thermocouple is a simple but important component of the AGA burner.  It is used in all types of gas appliances that have pilot lights – water heaters, furnaces and gas heaters. The probe of the thermocouple is placed in the stream of the pilot flame. When heat is applied to the probe it produces an electric current which lets the burner know that the pilot light is lit. If the burner was lacking this safety device, the thermostat could turn on the gas when the pilot light was out. Without the pilot light to ignite the gas, your house would fill with highly combustible gas.

You can see in the picture above that the probe is burned through. This is from years of being exposed to the pilot flame. Propane burns hotter than natural gas so propane AGA’s tend to go through thermocouples faster than natural gas.

What I learned from this episode:

  • Thermocouples are common and can be purchased from your local hardware store.
  • AGA’s use metric nuts to fasten the thermocouples in place.
  • Hardware stores in the US do not typically carry metric thermocouples.  I understand that UK hardware stores do carry metric thermocouples.
  • Foodservice equipment repair companies also have thermocouples in stock and may carry thermocouples for Garland equipment that are metric however, the part I tried did not work because the nut on the valve end was too small.
  • The threads on the valve end are M10 for the Teddington Mk 1.
  • I purchased the Thermocouple from AGA Thyme in Charlotte, NC. It was part number A1291 and it fit the old Teddington Mk 1 burner that I have.
  • agafixspares.com in the UK also sell universal thermocouple kits. The 600 mm universal model was recommended for the AGA GC model.
  • The A1291 came with an assortment of split nuts for the valve end. The larger M10 worked for me. A split nut cannot make seal, therefore it appears that the valve end of the thermocouple on the Teddington Mk1 does not need to be sealed. 
  • Swapping out the thermocouple was fairly easy however please involve a professional technician and do not rely solely upon the advice in this blog to repair your AGA.

Old thermocouple pictured above.

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