On Wed, 31 Dec 2014 09:00:35 -0600, dpb wrote:

On 12/31/2014 6:21 AM, Pat wrote:
...

Congratulations on fixing the problem. However, from an education
point of view, your statement that the flame sensor is just a hunk of
stainless steel is NOT correct. Google "thermocouple" and see how
they work. The current does not go through the flame. It is
generated by two pieces of dissimilar metals creating a voltage which
then causes a tiny current to flow and be sensed. They can and do go
bad.

Flame sensors of this type are _not_ thermocouples and indeed the
current is carried by the flame (actually ions produced by the
combustion process). Thermocouples are also used, but they're entirely
different.

It is correct, however, that the flame detector is quite a bit more than
just a chunk of SS...

http://www.gayesco.com/Prod_Flame_Rods.htm
Thank you for the education. I was not aware of that type.