Common Furnace Problems
No Heat
Most heating system
failures are caused by
thermostat malfunctions,
a tripped circuit
breaker or blown fuse,
or --in the case of
combustion furnaces-- a
pilot light that has
gone out. If the heat
doesn’t come on even
when you adjust the
thermostat to a setting
above room temperature:
1) Be sure the
thermostat is set to
"Heat" (if yours is a
heating and cooling
system). If it isn’t,
turn it to "Heat."
2) Be sure the furnace’s
circuit breaker is on or
that its fuse has not
blown. Check both the
main electrical panel
and any secondary
sub-panels that supply
power to the unit. If
the circuit has blown or
tripped, reset the
circuit breaker or
replace the fuse. If the
circuit blows again,
there is a probably a
short in the electrical
system providing power
to the furnace. Call an
electrical contractor.
3) Be sure the furnace’s
power switch is turned
on; it is usually
located next to or
inside the furnace
cabinet. If it isn’t on,
turn it on and wait a
few minutes for the
furnace to engage.
4) The motor may need to
be reset because of an
overload. Look for a
RESET button near the
blower motor's housing
and, if you find one,
press it. If nothing
happens, wait about 30
minutes for the motor to
cool, then try the RESET
button again.
5) Turn off the power
to the furnace at the
main electrical panel or
sub-panel. Look for a
fuse in the power
switch. If there is one
there, it may have
blown. Replace the fuse
(be sure to follow
instructions in your
owner's manual). If you
don’t have an owner's
manual or are not clear
about what it will take
to do this,
call us today.
6) With a gas furnace,
the pilot light may have
gone out or the gas
valve may be shut off.
Check the furnace's
ignition, as discussed
below.
7) If it still doesn’t
work, be sure the
thermostat isn’t faulty.
8) If none of this
works, call a
heating contractor or
furnace repair
technician.
Insufficient Heat
If your furnace runs
and provides some heat
but not enough, be sure
nothing is blocking the
flow of warm air.
1) First be sure the
thermostat is set
properly. Try raising
the set temperature 5
degrees and waiting a
few minutes.
2) Be sure the room
heating registers are
open.
3) Check the furnace
filter. If it's dirty,
change it .
4) If these simple steps
don't work, have a furnace
repair technician
check out your
system--either the
blower isn't working
properly or the system
is out of balance.
Furnace Turns On And
Off Too Often
If your furnace
cycles off and on too
frequently, the problem
is likely to be with the
thermostat--especially
with a combustion
furnace. See the
thermostat-related
problems below for
information on repairing
this problem. When an
electric-resistance
furnace or heat pump
turns off and on too
frequently, the problem
may be that the unit is
overheating because of a
clogged filter or blower
that is malfunctioning.
Try cleaning or
replacing the filter. If
that doesn't do the
trick,
call a furnace repair
technician.
Furnace Rattles
If the furnace makes
rattling noises when it
runs, be sure the cover
panels are screwed on
tight. If they aren't,
tighten them. Other
noises may be coming
from squealing belts, or
rattling ductwork.
Air Ducts Are Noisy
Many heating ducts
are metal, so they
conduct noise quite
readily from the
air-handling unit to
your rooms. To break the
conduction of sound, you
can have a heating
contractor insert
flexible insulation
ductwork between the
furnace or air
conditioner and the
ductwork runs.
If you hear a pinging
or popping sound coming
from the ductwork, this
may be caused by thermal
expansion or by air
blowing past a loose
flap of metal. Track
along the duct runs,
listening for the sound.
If you find it, make a
small dent in the sheet
metal to provide a more
rigid surface that’s
less likely to move as
it heats and cools.
