Ok,

I changed the main fan board, and still the exact same condition happens.

Even though the thermost is off, even disconnected, as soon as I turn the
main toggle switch for my furnace, both main blower fan and exhaust fans
immediately begin and nothing else happens.

I just unplugged on leg from the high limit switch, then one leg from the
low limit switch then both together

Same, nothing.
Any suggestions?

Thanks
73







" Tuuk" wrote in message
...
Hi

Thanks for all the advice. And I have tried all those. I took the
condensing fan blower out and cleaned out that housing behind it and
re-siliconed it. It did have some gunk in there but not enough to cause a
clog. But now that is clean and when I reinstalled it the exact same thing
happened. What is troubling me is that even if the thermost wires are
disconnected from that board what happens is both man blower and exhast
blower simply are the only things that run. Instantly. No sequence of
events eg blower starting, then ignigters starting then main blower after
heat exchangers heats up. None of that. I jumped that float switch and
those vacume hoses I sucked and blew through them and I can hear the
switches working, but same thing happens, nothing happens with that
honeywell smart valve, no gas. I checked all the intake air pipes and
exhaust pipes, nothing clogging. While everything leads me to believe it
is the board so I bought another for 80 dollars and will replace that
board today. I will take a photo of the board and one by one replace those
wired and connections and try that. I was hitting those relays on the
board and still nothing.

Seems some are upset because of my posts of my antenna and my sauna and
garden,,,, well coincedently enough I have in my basement the sauna and
steam bath thing I also installed and it was that very night that me and
the missis were steaming it up in the sauna and steam bath and I think
maybe there was moisture in the air that evening as that was the evening
it failed.

To answer a question about the lights, my friend's furnace has the idiot
lights where it blinks signifying what has failed, mine has no lights on
that board, I think mine was the model before his, mine is about ten years
old. I am going to replace this main fan relay board and see if that
solves the problem, I can return the board if the same problem remains and
start replacing the next part after that until something works right. I
replaced the thermostat with the old one and same problem.

Thanks for the advice and tips. As I have said, I know there is a lot of
knowledge in this group, I have benefited from it before and will again,
as my server doesn't have active newsgroups like HVAC or Furnace or any of
the other crazy things I have asked about. Lots of knowledge here, thanks.
And i cannot wait until someone asks a question about their furnace, or
their sauna rocks, or their tower, or their garden,,, because I will be
the first to answer.

73






"dave" wrote in message
...
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?