I'm having a problem with my furnace that I hope someone can shed some
light on. The furnace will run and then usually get to the desired
temperature set by the T-stat and stop. Then when the T-stat thinks
it should run again the the T-stat will show that the furnace is
running (it's an electronic T-stat), but the furance will not kick on.
If I am near the furnace, I can only hear a real faint buzzing sound
(which goes away if I shut the power off to the furnace). If I either
turn the T-stat off and on a few times or turn the power to the
furnace off and then on, the furnace will usually kick on (until the
next go around).
It seems to be a furance issue and not a T-stat issue, but I'm looking
for some help. Unless it is something really easy to fix, I plan on
calling a repairman, but I would still like to be knowledgable of the
problem beforehand.
It is a forced air Lennox furnce about 18 years old. I will mention
too that it started doing this a couple of days ago soon after I used
the electrical outlet on the furnace to power a shop vac (I rarely use
this outlet -- and I don't know if this would be related anyway).
Thanks.
Jim

Jim...
I'll try to help while the other boys are fighting it out.
First if it's an oil furnace ( you didn't say) it could be what you're
hearing is the motor trying to start. When you play with the stat it
will at some point, start the burner depending on the inrush of current.
It could also be that the motor isn't starting and what you're hearing is
actually the spark from the electrodes. It'd be faint and almost sound
like a hum. If this unit is gas, you'd need to continue to hope the
other guys put down the gloves and try to help as I've had no training in
gas furnaces. I've had since '75 on oil but up here in Malone NY, no one
has gas.

Doug