" Tuuk" wrote in message
...
Hi

I have the Keeprite 075 condensing gas furnace. Only about 10 years old.
Honeywell pro 8000 thermostat. NUGM100EHB1 is the furnace.

My question is what happened all of a sudden yesterday when I think I had
a bit too much humidity in the air, why did the furnace fail?

Now when there is a call for heat on the thermostat, what happens is both
blowers run only. The exhaust blower venting out runs immediately on start
up, the main house blower starts immediately on start up. But no clicking
from the honeywell smart valve, no sparking or ignighting beginning or
trying. Nothing else is happenening. No gas is going through the valve, no
obstructions in either intake or exhaust piping. I just vacuumed
everything out, I changed thermostates to the old one, same thing happens.
I suspect either the motherboard which has no lights to blink to show
alarms, or the gas valve which I had to replace couple years ago, But back
then at least the igniters would light up and shut off immediately, told
me it was a gas valve issue so replaced that and worked. All else looks
clean and I smacked as many relays as I could see, checked all the tubes
to see if connections are ok and seems ok. Even when thermostat is turned
off, disconnected, when I turn the furnace on it only immediately starts
up the both blowers and nothing else, no clicking, no safeties going on
and off, no nothing. Anyone here have a suggestion other than hiring an
HVAC contracting firm to come in and give me estimates? I know a board is
about 50 bucks, easy to replace, gas valve is about 150 easy to replace,
what ever sensor should be cheap and easy to replace. Any suggestions as
to what to try next?

Thanks Hams, I know this is off topic, but I have gotten good advice from
this group before and there are no furnace newsgroups of any kind on my
server.
Thanks for any advice or tips or links
73



When you say no lights to blink - do you mean it has no lights on the board
to do that
or do you mean there are lights on the board but they do not light up.
If the latter, it would certainly seem to be the board, if the former then,
darn, no help there.
Having had a similar problem my first replacement item would be the
motherboard.
Normally the vent blower comes on to purge the system for a few seconds,
followed of
course by the igniter, then the gas valve and after a short warm up the main
blower fan.
As both fans and start at the same time and nothing else is happening I am
thinking
the mother board is at fault.
Like you say, easy to replace and not to expensive and from the sound of the
problem
I would guess that is a good starting place.
I have a spare board and whenever I have a problem I use it for trouble
shooting.
If I replace it and get the same problem, then, I am off in search of what
is really
causing the problem.
As a side note, the earlier problem with the gas valve could have also been
a motherboard.
If the vent blower starts, then the igniter lights and then shuts down
either the motherboard
did not sense igniter heat or it did and then did not send the signal to
open the gas valve.
In your case it worked like it should but the valve did not open. It could
have been a bad
igniter sensing circuit or a bad valve opening relay however. Just something
to keep in mind.
Good luck with your problem.
Not a licensed furnace guy or anything, just have to do it all myself living
as far out in the
boonies of northeast Montana as I do. You learn to do this stuff or freeze
during the winter.


K7SAM