SERVICE AND TECHNICAL SUPPORT MANUAL
Gas Furnace: N9MSB
Specifications subject to change without notice.
16
440 04 4413 00
2. Remove blower door.
3. All factory wires can be left connected, but field
thermostat and accessory wiring may need to be
disconnected depending on their length and routing.
4. If the vent and combustion air pipe passes through the
blower compartment, it will be necessary to remove the
pipes from the blower compartment.
Disconnect the vent and combustion air pipe by:
a. Loosen the clamps on the vent couplings and
combustion air pipe external to the furnace.
b. Separate the pipes from the couplings and move
them aside.
c. Loosen the clamps on the vent couplings and
combustion air pipe located on the blower shelf.
d. Separate the pipes from the blower compartment and
set aside.
e. Remove the couplings from the pipe adapters and set
aside.
f. After servicing the blower, reverse steps a through e.
g. Tighten all clamps 15 lb
−
in.
See
Figure 8
for steps 5 through 14.
5. Remove screws securing blower assembly to blower
shelf and slide blower assembly out of furnace. Detach
ground wire and disconnect blower motor harness plugs
from blower motor.
NOTE
: Blower wheel is fragile. Use care.
6. Clean blower wheel and motor by using a vacuum with
soft brush attachment. Be careful not to disturb balance
weights (clips) on blower wheel vanes. Do not bend
wheel or blades as balance will be affected.
7. If greasy residue is present on blower wheel, remove
wheel from the blower housing and wash it with an
appropriate degreaser. To remove wheel:
a. Mark blower wheel location on shaft before
disassembly to ensure proper reassembly.
b. Loosen setscrew holding blower wheel on motor
shaft.
NOTE
: Mark blower mounting arms and blower housing so
each arm is positioned at the same hole location during
reassembly.
c. Mark blower wheel orientation and cutoff plate
location to ensure proper reassembly.
d. Remove screws securing cutoff plate and remove
cutoff plate from housing.
e. Remove bolts holding motor mounts to blower
housing and slide motor and mounts out of housing.
f. Remove blower wheel from housing.
g. Clean wheel per instructions on degreaser cleaner.
Do not get degreaser in motor.
8. Reassemble motor and blower wheel by reversing items
7b through 7f. Ensure wheel is positioned for proper
rotation.
9. Torque motor mounting bolts to 40 +/
−
10 lb
−
in. when
reassembling.
10. Torque blower wheel set screw to 160 +/
−
20 lb
−
in. when
reassembling.
11. Verify that blower wheel is centered in blower housing
and set screw contacts the flat portion of the motor shaft.
Loosen set screw on blower wheel and reposition if
necessary.
12. Spin the blower wheel by hand to verify that the wheel
does not rub on the housing.
13. Reinstall blower assembly in furnace.
Figure 8
Blower Assembly
A11584A
SET SCREW
MOTOR WHEEL HUB
MOTOR SHAFT FLAT
A11584B
SCREW
MOTOR ARM
GROMMET
A11584C
SCREW LOCATION
BLO HSG ASSY
BRACKET
BRACKET
ENGAGEMENT
DETAIL
A
A11584D
SEE DETAIL
A
POWER CHOKE
BRACKET
SCREW
(GND)
BLOWER HSG ASSY
MOTOR, BLOWER
WHEEL, BLOWER
CUTOFF, BLOWER
A11584E
OR CAPACITOR
WHEN REQUIRED
