Defective Thermocouple?

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    • #278271
      Avatar photoGilbert Chacon

        Two months ago I replaced the Thermocouple on my HydroTherm Gas/Steam Furance. The old Thermoncouple was 5 years old. Last night the pilot light went out. I tried to relight it – it wouldn’t stay lit – I cleaned the Thermocouple and the orifice of pilot gas line and again tried to relight the pilot light – still wouldn’t stay lit.
        I purchased a new Honeywell Thermocouple and installed it. This time the pilot light stayed lit. In the past Thermocouples have lasted for 4 to 6 years – the one I replaced lasted 2 months. Was this Thermocouple defective or could there be some underlying problem that is causing the Thermocouple to fail?

      • #298166
        Avatar photonicktheplumber
        Participant

          Wally,

          Like any other mass-produced device, including light bulbs, thermocouples may be defective and fail prematurely.

          That being said, other things can cause failure. I’ll name a few. The control valve could be faulty, but the fact that the problem resolved after a new TC was installed clears that suspect. Two other culprits deserve interogation…1) a kinked TC tube (connects to the control unit); and a excessively hot pilot flame (can damage the TC itself). Both are easily checked.

          NtP

        • #298167
          Avatar photoSelgas
          Participant

            Thermocouples can last 5 minutes or more than 5 years as they are a mass produced item, however check to see if the one you have has a larger than normal bulb in the area just under the gas valve as these one have a wax filled saftey cut off and will shut down if the main flame spills out the front panel for any reason such as a blocked flue etc.
            If this is the case then get the services of a suitably qualified gasfitter to correct your problem do NOT attempt this repair work yourself.



            Selgas Services Ltd
            Craftsman Gasfitters, Plumbers, Electrical Service Technicians

          • #298168
            Avatar photoWally
            Participant

              Nick and Peter,

              Thanks for your help. I’m hoping it was just a defective Thermocouple. I didn’t find a larger than normal bulb on the old Thermocouple or the line kinked. Not sure about the excessively hot pilot light – I’ll keep that in mind if the new Thermocouple fails in the near future.

              Wally

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