"Paul Batozech" wrote in message
...
Laurie Forbes wrote:

I have a Trane XL90 furnace (high effic, two stage) that goes into a
fault
condition every once in a while and will not generate heat until reset (a
big pain especially if it happens in the middle of the night). Was
wondering if there are any furnace gurus out there who might be able to
advise me. The fault code displayed means either a grounding or igniter
problem but I have checked both and nothing seems amiss. It sounds then
it
may be a controller board problem but I don't wish to replace it on spec
as
they want about $500 for the thing. Actually stopping a Trane is pretty
easy in my case

All help appreciated....

Laurie Forbes

--

Before you spring for a control board check the flame sensor. Modern
glow plug ignited furnaces don't use a thermocouple for flame sensing as
was done in the older standing pilot scheme. There should be a short
metal probe that is placed so one of the burner flames is in close
proximity, a circuit on the control board senses it's resistance to
ground which will change in the presence or absence of flame. These
tend to get a light coating of dirt on them over time and will hold out
the gas valve.

Thanks Paul but I don't think that's my problem as the furnace does not get
to that stage before the problem occurs. What happens is the inducer starts
and ramps up/down normally, the fault condition then occurs just at the
point the ignitor would normally begin to heat up. At that point, the
inducer stops, the blinkenlight flashes (9 times) and the blower comes on
and stays on.

I think I'll try replacing the ignitor on spec but it may be months before I
know if it has done any good as the furnace can go that long now without a
problem.

Laurie Forbes