On Sun, 23 Oct 2005 16:07:42 GMT, "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

How old is the unit? It might be a warranty issue.

If it has a silicon carbide hot-surface ignitor, go to your local
supply house and get two more - one to replace, and a spare on hand.
Much cheaper than a new control board - but remember that they are as
fragile as porcelain. There's a reason they are shipped in a sturdy
box well packed in foam.

When I last did HVAC full time these were just coming on the market,
and I always had a few on the truck. Now we just put in a new furnace
here that has one, and I need to go get a spare for the house.

The failure mode is for them to crack across the element and work
part of the time - then after a few cycles they get hot and expand a
bit and the crack opens before the gas lights off. You can see the
sparks across the crack. The controller sees the open ignitor and
trips a fault code blinkenlight, and that's one you have to unplug the
furnace to reset.

-- Bruce --

--
Bruce L. Bergman, Woodland Hills (Los Angeles) CA - Desktop
Electrician for Westend Electric - CA726700
5737 Kanan Rd. #359, Agoura CA 91301 (818) 889-9545
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