This page will help you replace your
blower motor on your forced air furnace.
The first thing you need to know is,
this can be dangerous, you can be
injured, you can loose your fingers, you
can be electrocuted, you can be burned
and you can be killed,
you can also burn your house down,
Master Plumber USA, and Thomas P.
Reardon can not be held reasonable for
anything that may happen
as a result of you following the
instructions on this and any other page
on this website,
You assume full responsibility for what
It is always best to have a professional
do this kind of work for you.
Now make sure the power to the furnace
is off, just because it is not running,
does not mean the power is off, just
turning the thermostat down does not
mean the power is off,
Make sure the power is off at the
circuit breaker, or the fuse is removed.
I have found that 90 percent of the time
circuit breakers and fuses are marked
wrong in the panel box, use a meter and
make sure the power is off.
an old Lennox furnace with a spark
ignition that is built in to the gas
can not give any instructions on how to
troubleshoot this gas valve.
If you have a furnace like this and need
help with the gas valve of ignition,
call a professional.
|The motor on this
furnace burned out, it is not always
apparent why a motor burns out, but in
this case it is a safe bet it burned out
because of neglect. People seem to be
under the impression, a gas fired
furnace never needs to be cleaned or
serviced, this is a big mistake that can
cause a very dangerous situation. All
furnaces gas or oil need to be inspected
and serviced every year
This is the blower motor compartment. In
this furnace the filter is located in
the blower motor compartment. The blue
thing shaped like a U is the filter. you
may notice how dirty it is. A filter
needs to be cleaned or replaced every
month, not cleaning or replacing the
filter as often as you should, shortens
the life of the furnace, the controls
and the blower motor, not to mention it
cuts down your efficiency.
|This is just a close up
of the gas valve. behind the gas valve
is the cam stat. The cam stat controls
when the furnace fires, stops firing and
turns the blower on and off.
OK, now it is time to cut some wires,
Are you sure the power is off, and no
one in the house will turn it back on?
This furnace has a 3 speed motor, others
have only a single speed motor, some
have a 3 speed motor but only use one of
the speeds. You want to cut the wires
going to the motor, cut close to the
motor, so that you have as much wire
left going back to the control as
possible. make sure you are only cutting
wires that go into the blower motor,
many blower motor compartments have a
high limit switch. you do not want to
cut the wires.
The whole squirrel cage housing needs to
be removed, on most furnaces there are 2
bolts one on either side that need to be
removed. Some are on the bottom others
are on the top, this one is mounted to
the top. Care needs to be taken not to
have the whole thing just drop.
Unfortunately this electrical box is in
my way, and will have to be removed in
order to get the squirrel cage housing
out, please see the following pictures.
Note the screws need to be removed from
the top I have a flexible drill bit
extension with a magnetic nut driver on
it, it makes getting at the screw heads
Now with the box hanging I can pull the
squirrel cage housing out and just push
the loose wire box out of the way. You
do not need to remove the box and all
I got it out and set it on the floor, it
this very small room, I can see just how
dirty this furnace really is by looking
at the following pictures you will see
what happens when you don't have your
furnace inspected and serviced every
You may find it hard to believe, but I
have seen worse. The blower motor could
not breath and was over heating on a
regular basses. And then in the middle
of the night, in the middle of a cold
snap, in Anchorage Alaska this blower
motor quit. If these people were not
home at the time, there whole house
would have froze, all there pipes would
have broken and even there toilets would
have cracked and would have needed to be
replaced, believe me I have seen it
happen. All for the cost of a filter.
||To remove the motor
from the squirrel cage, first remove the
ground wire, then remove the 3 bolts
that hold the mounting bracket to the
squirrel cage housing. then turn the
whole thing over.
the side, where the motors shaft comes
through the squirrel cage, there is a
1/4 square nut. loosen this nut as far
as you need to, allowing the shaft to
move. Sometimes even with the nut
removed the motor shaft will not move,
if this happens use some king of liquid
wrench. If you have to tap it out, be
careful not to mushroom the shaft end,
because then you will never get it out.
Now flip it over again and you have the
old motor out. Make notes where the
motor brackets are located on the old
motor before you remove them. Most new
motors do not come with new brackets,
you will need to use the old ones. there
are many different types of brackets. if
your new motor has oil ports you want to
be sure they will be facing up when the
blower motor is back in place.
||Now you will need to
put the bracket on to the new motor.
It's important that you replace the
motor with the correct size motor, you
can use the old motor as a guide or you
should be able to get the information
from the plate inside the furnace.
because we do so many motors and there
are so many different brands, we use a
universal, motor. We still have to use
the right size in horse power and the
shaft has to be the same size, but the
motors we use can be used for either
clockwise or counter clockwise
This is the box this one came out of.
note the brand name and horse power and
it also tell us the right capacitor to
use. replacing the motor with out
replacing the capacitor is foolish make
sure to replace the capacitor when you
replace the motor.
||The label attached to
the new motor tells you, what wire is
what, this is very important, because
the wires may not be the same colors as
the motor you replaced.
Make sure the bracket is on the motor
correctly and that the bracket will not
interfere with the wires and that the
wires will reach the ends you cut off
before. In the images below you will see
the wrong way for the squirrel cage to
be positioned. to far to either side
will rub and make a lot of noise and
cause damage to the squirrel cage and
housing. make sure it is centered and
|By Thomas Reardon