On Wed, 19 Jan 2011 19:21:51 -0600, Vic Smith
wrote:

On Wed, 19 Jan 2011 17:12:51 -0700, Tony Hwang
wrote:



Hi,
Flame sensor o/p is by the millivolts. My problem was with HSI couple
times burning out. Flame sensor was never replaced.

I replaced my HSI once, and have a spare on hand.
When I was looking up HSI - never heard the term - I ran across this,
which is a pretty good basic explanation of common furnace light off
sequence.
http://arnoldservice.com/Troubleshoo...g_Problems.htm

One thing isn't clear about Bobo's problem, and that's how long the
furnace fires before shutting down.
My Rheem would only fire for a few seconds when the flame sensor
needed cleaning.
Bobo seemed to indicate his is firing much longer.
If that's true I take back everything I said.

--Vic

Yes, the gas stays on a little longer in mine, and the duration
varies from say, ten to twenty seconds. After it started working again
this morning I turned the heat down before I went to work.. When I
returned home the problem started again. As it seemed to work fine
when there wasn't much time between burns I thought warming it up
might help so I put an electric heater in front of it for awhile and
it's running fine now. I mailordered a flame sensor when it was
running good this morning. I hope that does the trick. The mailorder
place has boards for $125. Hopefully I won't be sorry I didn't order
one. I sure have learned allot about modern furnaces the last couple
of days.
I think the flame sensor produces voltage when hot so it would be a
tough thing to simulate.