On Fri, 16 Dec 2011 18:20:26 -0500, Tuuk wrote:

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

Is there a thermostatic switch on the hot air manifold?