"blueman" wrote in message
...
"Dimitrios Paskoudniakis" writes:
"blueman3333" wrote in message
...
We have a "York Diamond 90" gas-fired furnace that was working well
until today.

There seems to be something wrong with the gas flow/valve, burner, or
sensor.

I can see the electronic ignition element turning white hot, then hear
the gas valve click on, then see the blue gas flames light for a
second or two before sputtering out. This cycle repeats itself several
times until, the system "gives up" (or I guess locks out) at which
point the blower just continues to blow cold air forever and no
further ignition attempts are made. The blower continues to blow even
if I shut off the thermostat

Interestingly, if I cycle off the power (even just for a second or
two), the furnace will start up normally and ignite the burners
properly. The burner will continue to fire for a *couple of minutes*
before blowing out at which point it goes into the (failed) cycle of
trying to relight a couple of times before finally giving up and again
leaving me in the stuck state with the blower blowing cold air.

Sometimes in the cycle of trying to re-light it will burn for a
few seconds before sputtering out. Also, sometimes, I hear the valve
clicking on-and-off a couple of times in rapid succession.

Now the other two gas furnaces are working properly, so I don't think
it is a supply problem. Also, I don't think it is a ventillation
problem
because it seems to burn fine for a few minutes with a nice blue flame
before suddenly sputtering out.

When I opened up the bottem panel (overriding the disable switch), I
noticed that after it locked up in the continuous blower position, the
diagnostic LED exhibited a pattern of 8 short (red) flashes -- I
believe
this simply indicates that the flame is lost 5 times within a heating
cycle which according to the online manual indicates either:
Low gas pressure (unlikely since other two gas
furnaces in the house work fine, right?)
Faulty gas valve
Dirty or faulty flame sensor
Faulty hot surface igniter (unlikely because the flame does
ignite, right?)
Burner problem

Any idea what might be wrong and how to fix?

Even if this is not a DIY fix, I would like to have some idea of what
the potential problems could be so that I can intelligently engage the
service person and make sure that I am not being taken

Thanks!

I once had similar symptoms (I have since moved).

I had a condensate pump, and it filled with "gunk" over time. I had a
contractor confirm this was the problem. He removed the pump, took it
outside, took a hose to it, reinstalled, and the problem resolved. Don't
actually know what the failure mechanism was, but this resolved it. It
happened again a year later, but I just cleaned the condensate pump
again.
When I moved, I left a note for the buyers, and included a description
for
them to rinse out the condensate pump about twice a year.

Don't know if this is the same problem as yours, but thought I'd share my
story.

Interesting, do you mean to say that a dirty condensate pump caused
the burner to shut down prematurely and then prevented it form
re-lighting properly? Because if so, I am sure that is the problem
because as mentioned in my subsequent post, I actually just installed
a condesate pump. Not sure how a downstream pump affects upstream
flame but I'm sure that must be it if you say you had the exact same
problem caused by a condensate pump...

I don't know how the dirty condensate caused the problem either. Once all
the side panels were removed from the furnace, one could see tubes for water
condensate. Perhaps a clog caused a backup, but I don't know how that would
cause the symptoms my furnace had.

Still it sounds similar. I just remembered that mine got worse when it
would run for a long while. I had a digital programmable thermostat, and we
had the temperature set lower overnight. When it came time to warm up the
temperature by the time we awoke, after running for a long enough period, I
would hear a rapid clicking noise coming from the furnace, then I saw the
flame go out. I would hear the motor continue to run for a little while
longer before it would shut off. Then after five minutes the system would
start up again. This was before the temperature reached its new higher set
point where the system should not have yet shut down.

Once we cleaned the condensate pump, the problem seemed to clear. In
addition to summer condensation from the A/C, I diverted central humidifier
wastewater into the condensate pump in the winter, so the pump was used all
year round.

Don't know if this will help, especially since you indicated your pump is
new.