SERVICE AND TECHNICAL SUPPORT MANUAL
Gas Furnace: (F/G)9MAE
Specifications subject to change without notice.
440 04 4700 00
25
!
WARNING
ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in personal injury, or
death.
Blower access door switch opens 115
−
v power to furnace
control. No component operation can occur unless switch is
closed. Exercise caution to avoid electrical shock from
exposed electrical components when manually closing this
switch for service purposes.
16. Downflow or horizontal furnaces with vent pipe through
furnace only:
a. Install and connect short piece of vent pipe inside
furnace to existing vent.
b. Connect vent connector to vent elbow.
17. Turn on electrical supply. If outdoor temperature is below
70
_
F (21
_
C), turn off circuit breaker to outdoor unit
before running furnace in the cooling cycle. Manually
close blower access panel door switch. Use a piece of
tape to hold switch closed. Check for proper rotation and
speed changes between heating and cooling by
jumpering R to G and R to Y/Y2 on furnace control
thermostat terminals. Turn outdoor circuit breaker on
after completing cooling cycle. (See
Figure 3
)
NOTE
: If R
−
W/W1 thermostat terminals are jumpered at the
time blower access door switch is closed, blower will run for 90
seconds before beginning a heating cycle.
a. Perform component self
−
test as shown at the bottom of
the SERVICE label, located on the front of blower
access door.
b. Verify blower is rotating in the correct direction
18. If furnace is operating properly, RELEASE BLOWER
ACCESS DOOR SWITCH. Remove any jumpers or
reconnect any disconnected thermostat leads. Replace
blower access door.
19. Downflow or horizontal furnaces with vent pipe through
furnace only:
a. Install and connect short piece of vent pipe inside
furnace to existing vent.
b. Connect vent connector to vent elbow.
20. Reinstall outer door.
21. Turn on gas supply and cycle furnace through one
complete heating cycle. Verify the furnace temperature
rise as shown in Adjustments Section. Adjust
temperature rise as shown in Adjustments Section.
Cleaning Burners and Flame Sensor
The following items must be performed by a qualified service
technician. If the burners develop an accumulation of light dirt
or dust, they may be cleaned by using the following procedure:
NOTE
: Use a back-up wrench on the gas valve to prevent the
valve from rotating on the manifold or damaging the mounting
to the burner assembly.
Refer to
Figure 9
.
1. Disconnect power at external disconnect, fuse or circuit
breaker.
2. Turn off gas at external shut-off or gas meter.
3. Remove outer doors and set aside.
4. Turn electric switch on gas valve to OFF.
5. Disconnect the gas pipe from gas valve and remove pipe
from the furnace casing.
6. Disconnect the connector harness from gas valve.
7. Disconnect Hot Surface Igniter (HSI) wires from HSI.
8. Disconnect Flame Sensor wire from Flame Sensor.
9. Support the manifold and remove the four (4) screws that
secure the manifold assembly to the burner assembly
and set aside. Note the location of the green/yellow wire
and ground terminal.
10. Inspect the orifices in the manifold assembly for
blockages or obstructions. Remove orifice and clean or
replace orifice.
11. Remove the four (4) screws that attach the top plate of
the casing to the furnace.
12. Raise top plate up slightly and prop it up with a small
piece of wood or folded cardboard.
13. Support the burner assembly and remove the screws
that attach the burner assembly to the heat exchanger
cell panel.
14. Remove wires from both rollout switches.
15. Slide one-piece burner assembly out of slots on sides of
burner assembly.
16. Remove the flame sensor from the burner assembly.
17. (Optional) Remove the Hot Surface Igniter (HSI) and
bracket from the burner assembly.
18. Check igniter resistance. Nominal resistance is 40 to 70
ohms at room temperature and is stable over the life of
the igniter.
19. Clean burner assembly with a brush and a vacuum.
20. Clean the flame sensor with fine steel wool (0000 grade).
Do not use sand paper or emery cloth.
To reinstall burner assembly:
1. Install the Hot Surface Igniter (HSI) and bracket in burner
assembly.
2. Install flame sensor on burner assembly.
3. Align the edges of the one-piece burner assembly with
the slots in the burner assembly and slide the burners
forward until they are fully seated in the burner
assembly.
4. Align the orifices in the manifold assembly with the
support rings on the end of the burner.
5. Insert the orifices in the support rings of the burners.
NOTE
: If manifold does not fit flush against the burner
assembly, do not force the manifold on the burner assembly.
The burners are not fully seated forward in the burner
assembly. Remove the manifold and check burner positioning
in the burner assembly before re-installing the manifold.
6. Attach the green/yellow wire and ground terminal to one
of the manifold mounting screws.
7. Install the remaining manifold mounting screws.
8. Check the igniter alignment. See
Figure 9
,
Figure 10
and
Figure 11
.
