Hi all,
I have a Lennox 90UGF Series Unit and it is not starting up. I raise
the thermostat temp a couple of degrees, and I can hear "something"
turning on (sounds like either the fan or it's simply getting power)
but I don't hear that "whosh" sound, even after it's been turned on for
a while. Now, I did neglect the air filter for a few months (totally
forgot about it) and when I replaced it yesterday, the old one was
pretty dark with dust.

Hope someone can help.

Rob