This is not the way ignition occurs. the way a pilot is sensed is
called flame rectification. the only thing that comes close to what
you are saying is the limit switch which has a totally different
purpose.

The sensor probably needs to be replaced. It's a safety-related item
and the repair should be done by a licensed professional.

this is true of any safety device such as the limit.


Hi, I agree with William and HvacTech2

I had the same kind of problem this fall, and I can tell you that the source
of the problem might not be obvious at all for a non professional.

In my case, the problem was at the furnace level.
The gas valve was defective and letting too much gas being burned, which
made the furnace overheat, and thus the limit switch (I am not sure it is
the correct name, it is the dial with 3 tabs) was shutting down the gas
burning when the temperature was too high, then the temperature would lower
and the switch would let the gas burning resume, and on and on...

Here is a forum with people that are friendly and willing to help you
pinpoint the source of your problem, if that is really what you want. I had
started a thread (which has diasppeared since then) on my problem back then
and I got lots of good info. I called for a tech anyway because I dont like
playing in those things, but I do like to understand how things work on the
other hand. When I called the techs, I knew that I had an overheating
problem.

http://ths.gardenweb.com/forums/hvac/

Good luck!