Our house was build in end of 1995 and we have two gas furnaces in the
attic -- one for each floor. We are the second occupants of the house.
The original furnaces are still in place and I have not had any
maintenance done on them over the last five years. I do regularly change
the filters every 4 months.
Over the last week or so, one of the furnaces has been making a
screeching metallic noise when it is about to turn off. The noise is now
loud enough where it can be heard downstairs. The unit does seem to be
Any pointers to what the problem could be?
Time for maintenance. Based on my experience (as a homeowner, not a
tech) anytime a mechanical item makes a noise like you describe, it
would be best to shut down that furnace before something more serious
Since the main moving part in a furnace is the blower fan, the sound
you hear is likely the bearings in the motor or the fan wearing on
each other. You hear it better when the fan stops spinning as it will
gradually slow down hitting the right frequency to attenuate the
sound. when spinning the noise is probably at a high enough frequency
you can't hear it with your ears.
If it is a bearing, and you continue to operate the furnace, the
bearing can eventually fail such that it welds itself together,
preventing the motor shaft from turning any longer. This will cause
the motor to overheat, and hopefully throw a circuit breaker on the
motor, or blow a fuse on the controller.
Best case, the motor may need to be replaced. Worst case, the stress
of driving that failing bearing over time has caused the controller to
be damaged. Considering the age of the furnace, that could mean
difficulty finding reasonably priced replacement parts leading to just
out and out replacing the furnace.
Only a HVAC tech is going to be able to tell you exactly what is going
on, so I suggest you call one before the thing finally fails when you
really need it, and you have to pay weekend or emergency rates for the
Thanks for your response. I live in the Roswell (suburb of Atlanta) and
just setup an appointment with Central Heating & Air (got that name from
homereports.com) for tomorrow. I am hoping that their techs will be
The furance is in the attic? If so, it's lying on it's side. Likely the
blower has come loose on the shaft and needs to be pushed back into postion,
and the lock nut tightened. Good luck though, usually [since H.O. refuse to
shut it off] the lock nut is just loose enough for the blower to move down
and nick or wear a groove in the shaft making it a bitch to move back. You
might be looking at a new motor [since the shaft is ruined,] and a new
blower wheel, [since the hub is now elongated and worn.]
Not a bad deal. Consider you didn't have to dispose of the hazardous "e"
waste, and you got a warranty. Not really bad at all considering you didn't
have to pull the furnace and take it the shop. [Like your car maybe.]
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