My wall heater is not functioning. I had a similar post last year, and this year the problem evolved. Attached is the kind of wall furnace that I have. https://drive.google.com/open?id=1hcXdkyu35Cb2nlOZ1bFaKysJ3pij6Pog

The pilot fire does stay lit. Turing the thermostat on does not kick in the burner. Thus, for the past winter, I have been shorting the two Th to start the burner, and then it works perfectly. However, this method does not seem to always work for me anymore this winter, and shorting the Th even puts off the pilot fire.

I have done some basic testing (the numbers are same as of last winter).

With burner off:

  • Pg to Pg: 360mv

With burner on:

  • Pg to Pg: 250mv.
  • Pg to Th: 225mv.

Wondering if this sounds like a faulty thermopile? I actually did put in a new one last winter, wondering if trying another newer one would help.

Thanks in advance!


The normal output for most thermopile devices is about 750MV. That is 3/4 volts. That 3/4 volts is not a lot of voltage to go from the thermopile through the wiring , furnace operating and safety controls, the thermostat, and back to the gas valve to actuate it. Any loose wire connection, dirty contact, old thermostat, the old gas valve, and even old thermostat wiring can lessen the voltage to open the gas valve. If the system is old and it looks old from the picture, replacing all of the items mentioned may be necessary. Also, all the items will usually have special contacts made for a powerpile device so if you are going to replace them make sure that they are made to be used in a powerpile system. Buy only quality parts made by a reputable parts company and not the "cheap junk" sold all over the internet. When you install the powerpile thermocouple make sure that 1/2 of it is enveloped by the flame and not just the top of the tip.

| improve this answer | |

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.