"Bill" wrote in message
ups.com...
Thanks for your informative and quick response, Greg.


Is their a way to isolate whether or not the intermittent failure
occurs from the gas side or the spark side?

Thanks.

Bill


Other than to throw parts at it, no.
This is one of those times when patience is required. Somebody may need to
just baby sit the darned thing for a while. Usually by jumping the stat
connections at the furnace, and watching it go through it's ignition
sequence with a voltmeter or two connected at the appropriate places a tech
will find the problem. Sometimes it may take some time though!
I had one I spent the better part of the day watching! A couple other techs
had looked it over and gave up. Those intermittent problems can really be a
problem sometimes.
Greg