Twice in the last two weeks, the pilot has blown out in our wall
furnace. We are having windy weather. When relighting pilot, I press
the transfer button on the relay, normally, after 15 seconds, the gas
valve relay will latch on allowing me to release the button and pilot
What is different now, AND NOT TYPICAL, is NOW, when I relight the
pilot, and hold button in for 2 minutes or longer, releasing the button
allows the pilot to turn-off, the gas valve relay did not latch-on.
Thwe thermocouple junction is being lighted by the pilot flame and area
is free of dust.
The only way to cause the relay to latch-on and keep pilot lighted, is
to hit the valve-relay body several times with the handle of a plastic
screw driver.Recently not-latching has happened twice.
What could be wrong? Is the thermopile [thermocouple] bad or is the gas
valve-relay bad? Or is something else bad?
Thanks for your thoughts. Dave_s
The general rule it to replace the easiest and cheapest part first. The
thermocouple is it. Before you replace it you might try disconnecting and
reconnecting it at the valve. This will sometimes clean a poor connection
and solve the problem.
And that would be from the "Rules of Hackery" guide? :)
Maybe 1 out of 100,000 times loosening and re-tightening will correct
the problem. In over 20 years I've never once encountered a system on
which this would have accomplished anything. I have heard others say
they had gotten a unit to work by "re-tightening", but invariably the
customers called back. IOW, the pilot may have held on that try even if
they hadn't touched the thermocouple. When the mV output is marginal
this is a common mistake among technician and homeowners alike. It's
just coincidence. The general rule is that if the connection was clean
when the thermocouple was installed, which would be indicated by the
thing actually working like it should afterward, then dirt can't
accumulate between the metal faces of the junction because it has no way
to get there. If on the other hand the connection is loose, then simply
tightening it can sometimes be the cure, and this isn't the same as
re-tightening. If it was already tight, then re-tightening isn't going
to cure a thing, though you can fool yourself into believing that it
did, that is, if you let yourself. Then again this is all immaterial, I
prefer to simply check the mV output rather than play guessing games
and/or engage in parts swapping.
The other day my seat belt light was irritating me, so I reached down
and pressed the latch button. The light went off at the exact same time.
I thought hey, you don't have to insert the clasp into the latch to turn
off the warning light. Next time I tried this it didn't work. It was
just a coincidence first time, but it was a very convincing illusion.
On my old in_the_wall HOLLEY Gas Heater, how can I test if the
thermocouple is OK? I have good multimeters. Do I just disconnect the
thermocouple from the gas-valve and measure the voltage when the
thermocouple is hot and also is cold? What should the voltage be when
hot and what when cold? Thanks Dave_s
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