SERVICE AND TECHNICAL SUPPORT MANUAL
Gas Furnace: (F/G)9MXE
Specifications subject to change without notice.
14
440 04 4311 08
ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in personal
injury or death.
There may be more than one electrical supply to the
furnace. Check accessories and cooling unit for
additional electrical supplies that must be shut off
during furnace servicing. Lock out and tag switch with
a suitable warning label.
!
WARNING
The electrical ground and polarity for 115
−
V wiring must be
properly maintained. Refer to
Figure 7
for field wiring
information and to
Figure 15
for furnace wiring information.
NOTE
: If the polarity is not correct, the STATUS LED on the
control will flash code 10 and prevent the furnace from heating.
The control system also requires an earth ground for proper
operation of the control and flame
−
sensing electrode.
The 24
−
V circuit contains an automotive
−
type, 3
−
amp. fuse
located on the control. (See
Figure 4
) Any shorts of the 24
−
V
wiring during installation, service, or maintenance will cause
this fuse to blow. If fuse replacement is required, use ONLY a
3
−
amp. fuse. The control LED display will be off when fuse
needs to be replaced.
Troubleshooting
Refer to the service label. (See
Figure 14
—Service Label)
The Troubleshooting Guide
−
Flow Chart (See
Figure 16
) can
be a useful tool in isolating furnace operation problems.
Beginning with the word “Start,” answer each question and
follow the appropriate arrow to the next item.
The Guide
−
Flow Chart will help to identify the problem or
failed component. After replacing any component, verify correct
operation sequence.
Proper instrumentation is required to service electrical controls.
The control in this furnace is equipped with a Status Code LED
(Light
−
Emitting Diode) to aid in installation, servicing, and
troubleshooting. Status codes can be viewed at the indicator in
blower door. The green furnace control LED is either ON
heartbeat, off or a code composed of 1 or 2 digits. The first digit
is the number of short flashes, the second digit is the number of
long flashes.
Figure 7
Heating and Cooling Application Wiring Diagram with Single
−
Stage Thermostat
115-V FIELD-
SUPPLIED
DISCONNECT
AUXILIARY
J-BOX
24-V
TERMINAL
BLOCK
THREE-WIRE
HEATING-ONLY
FIVE WIRE
NOTE 1
NOTE 2
FIELD-SUPPLIED
DISCONNECT
CONDENSING
UNIT
TWO
WIRE
FURNACE
C
O
N
T
R
O
L
R
G
COM
W
C
R
G
Y
GND
GND
FIELD 24-V WIRING
FIELD 115-, 208/230-, 460-V WIRING
FACTORY 24-V WIRING
FACTORY 115-V WIRING
208/230- OR
460-V
THREE
PHASE
208/230-V
SINGLE
PHASE
BLOWER DOOR SWITCH
WHT
BLK
WHT
BLK
NOTES:
Connect Y-terminal in furnace as shown for proper blower operation.
Some thermostats require a "C" terminal connection as shown.
If any of the original wire, as supplied, must be replaced, use
same type or equivalent wire.
W
Y
GND
THERMOSTAT
TERMINALS
1.
2.
3.
A11387
For an explanation of status codes, refer to service label
located on blower door or
Figure 14
, and the troubleshooting
guide which can be obtained from your distributor.
Retrieving Stored Fault Codes
NOTE
: Fault codes cannot be retrieved if a thermostat signal
(24-V on W, Y, G, etc.) is present, or if any delays such as
blower off-delays are active.
The stored status codes will NOT be erased from the control
memory when 115- or 24-V power is interrupted. See the
Service Label (See
Figure 14
) for more information. The most
recent fault code may be retrieved as follows:
1. Leave 115-V power connected to furnace.
2. Observe the status LED through the blower door (the
lower door on upflow applications) indicator. Refer to the
Service Label (See
Figure 14
) to interpret the LED.
3. Remove the Main/Control door (the upper door on upflow
installations).
4. BRIEFLY (2
−
3 seconds) disconnect and reconnect ONE
of the main limit wires.
5. The LED will flash the last stored fault code. Refer to the
Service Label (See
Figure 14
) to interpret the LED.
