possibley the draft inducer motor.

"N Harrison" wrote in message
...
My forced air Gas heater makes a high-pitched whining noise but I'm
pretty sure that it's NOT the blower! If anyone has heating a/c
savvy, please read on.

We are in a house in Chandler, AZ, that is about 4 years old. It has
forced air gas heating. I hear that it's been done cheaply: both the
heater and air conditioner are located in the attic (the a/c
compressors are outside, the blower etc. are in the attic). People
say this is a bad design but cheaper for builders, so we're stuck with
it.

We bought the house in during the summer, so we tested the a/c and it
works flawlessly. I also tested briefly the heater enough to notice
that it worked, but I was so excited looking around our potential new
dream home I didn't notice the high pitched squeal it makes.

So around November, when you have to start using the heater in this
part of Arizona, I switch the thermostat over to heat and am appalled
when I hear this high pitch whining noise that appeared to coincide
with the heater. I figured, no problem, it's probably an unlucky
small vent in a duct that's making this noise, and I'll just find it
and go over it with duct tape. But then I notice that it doesn't
coincide with when the blower runs.

Here's its behavior: when the heater lights up to warm the air BEFORE
the blower starts, the whine begins. It continues while the blower is
blowing, but then about 2 minutes before the blower stops it stops. I
assume this is the same time the fire goes out and it stops actively
heating while the blower continues to blow over the still hot metal
parts.

Does anyone have any idea what is doing this? I could swear it seems
to be coming not from the heater itself but from some ductwork about
20 feet away in the attic (inaccessible to me), and this makes no
sense to me because as I said, it doesn't start and stop with the
blower, so I don't think it's some kind of air movement noise. (I
could be mistaken. In the small attic trying to locate the source of
the whine is like trying to find a cricket--I can't really tell where
its coming from.)

Any ideas?