Problem: Furnace makes
unfamiliar noises when operating.
Background: Sometimes homeowners think their
forced-air furnaces need to be replaced because they make
strange noises. But the cause may be a simple mechanical
problem with the motor or fan within the blower system.
Sometimes making simple adjustments and / or replacing a
part will solve a strange noise problem.
What to do: Turn off the power to the furnace,
remove access panels, and make a careful examination of
the blower area. Check to make sure that the drive belt
between the motor and the blower has proper tension, is in
alignment, and is not cracked.
Also check the pulley on the motor, making sure that it is not
loose on the shaft, has worn grooves, or is dirty. If
loose, retighten any set screws. If worn or dirty, remove
the belt, clean the pulley, and sand down its interior
sides. Also check the pulley on the blower fan. Spin the
blower to check for sound which may be caused by something
inside. If the fan is rubbing against the housing, it
needs to be adjusted and your best bet is to call a
technician. Push and pull on blower pulley to check for
end-play. If excessive, shaft collars need to be adjusted.
Special advice: A blower that needs oil may also
make noises. Follow owner manual instructions to oil.
Sometimes oil-less bearings wear out and need replacement.
To see if the motor is making the noise, re move the belt
and run the motor; the motor may simply need oiling, but
motor bearings may still make noise.
If so, decide if you can live with the noise or if you
want to replace the motor. A dirty furnace filter can also
cause noise; clean the filter as recommended.
Helpful hint: If the
burner of a gas furnace makes an unusual noise, the gas
input amount may not be correct, or it may be getting too
much primary air. In either case, contact a service
technician. Also, contact a technician immediately if the
walls or windows in your home sweat excessively. The
furnace may not be getting enough ventilation or the flue
pipe may be blocked (see
Appliance Venting Faulty).