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I was looking at my furnace a couple of days ago and I notice one thing: there is something red hot there where the spark igniter and the thermocouple assembly is. I can hardly see it and I am not sure what component is that but I was just wondering if this is normal.

This is what I have for thermocouple and spark igniter enter image description here here is what is hot red. I looked again from a different angle. I think that the pilot light stays on for as long as the thermostat asks for heat. After that it turns off, that does happen I am not concerned about that. I am just wondering if, after the burners are lit, the pilot light should still stay on. I see no sense in that. enter image description here Here is the electrical scheme for my igniter
enter image description here

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This is an edited answer

After reviewing the additional information provided above along with relevant information obtained from this post: What is wrong with my gas furnace? I have entered my answer below.

The "something red hot" in your furnace is apparently a "hot surface ignitor". The red hot glow is produced by passing current through the ignitor and is the intended function.


Now, to my concern for your safety:

I originally stated that there did not appear to be a thermocouple on your furnace. While I maintain that there is indeed no thermocouple, I also add that the hot surface ignitor is likely monitored by the control module in the furnace. While I am not intimately familiar with this furnace nor the application of such an ignitor, I can safely presume that the control module senses the resistance of the ignitor and can tell this way whether the pilot light is lit or not.

One way to verify my assumption about the control of gas flow would be to remove the connector for the ignitor while the unit is off and then see if you can hear the gas flowing (or can otherwise sense the gas flow - temperature, smell) when a demand for heat is made. Just make sure you do this quickly and safely! (i.e. Do not reconnect the ignitor unless the thermostat is off!!!)

  • Yes the picture shows exactly the device that I have. I have added the electrical scheme for this – MiniMe Dec 15 '14 at 23:30
  • ok I have marked with red what is red hot. Please see the clarifications that I just added to the initial post. Note that the electrical diagram says sensor but that is really a thermocouple (I guess it is under the white ceramic coating) – MiniMe Dec 15 '14 at 23:56
  • Yes I do have an electronic gas control circuit but we are digressing here. My question is about the pilot light – MiniMe Dec 16 '14 at 0:13
  • OK so based on your edit the pilot flame should stay on as long as the burners are on. Is that a correct interpretation of your edit? I think that I shortly run that test a while ago and I did not hear the gas but I did hear some noise that was coming from the valve. I was to scared to keep it longer so I stopped the whole experiment. I will try it again over the weekend. And yes indeed it works as you described, somehow the control module senses a current that flows between the ignitor and ground (so it senses the resistance you mentioned above) – MiniMe Dec 16 '14 at 0:31
  • Yes, I believe that the glow must be present for the pilot to stay lit. If you are uncomfortable about the valve making noise, please call in a professional. There is a time and place for DIY but when dealing with a potential hazard it is always best to be sure. – Gabriel Dec 16 '14 at 0:37

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