On Oct 15, 8:15 pm, "Joseph Meehan"
wrote:
"Steven Andrade" wrote in message

...

I almost thought that, but normally under the conditions described a
bad
thermocouple would not allow the pilot to say on

When I try to turn the pilot adjustment knob to "ON"
the pilot light goes out even if when the pilot has been
burning for 20 min (hot). The knob in
question has three settings - 1. Off, 2. Pilot, 3. On.

Sounds exactly like the TC to me.

In my experience (limited) when the thermocouple is bad, the pilot light
will stay on as long as the "button" is pressed. When the (light) button is
released about about 30 seconds, with the switch still on Pilot (you can's
move it off with the button depressed) the pilot will go out. The
thermocouples (as I recall) protect not just the main burner, but will also
shut down the pilot. Frankly it has been a long time since I had had to
light a pilot light I could be remembering that wrong. If I am then if a
pilot blows out, then gas will be released into the room.

--
Joseph Meehan

Dia 's Muire duit


You are correct if the thermocouple failure mode is is either a) bad
or b) good. Considering how they operate, the dissimilar metal
junction actually generates the small voltage to power the pilot gas
flow widget and permit the main valve to function (round of applause
here for Dr. Peltier!). But there can also be c) intermittant failures
(rare) from junction welds going bad. Makes sense then to cheaply
eliminate a), b) and c) all at once and then get into the tougher
diagnostics if you're unlucky.
Kind of like don't overhaul the carburetor unless you know your fuel
is fresh and frisky. Cheers,

Joe