Troubleshooting - International comfort products F9MXT0401410A Service And Technical Support Manual

SERVICE AND TECHNICAL SUPPORT MANUAL
WARNING
!
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.
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
Figure 7 Heating and Cooling Application Wiring Diagram with Single−Stage Thermostat
BLK BLK
WHT WHT
GND
115-VOLT FIELD-
SUPPLIED
FUSED
DISCONNECT
For an explanation of status codes, refer to service label
located on control 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.
14
NOTE 2
W C
FIVE
WIRE
THREE-WIRE
HEATING-
ONLY
W2
COM
W/W1
NOTE 1
Y/Y2
JUNCTION
BOX
R
CONTROL
BOX G
24-VOLT
TERMINAL NOTES: 1.
BLOCK
FURNACE
Specifications subject to change without notice.
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 be a
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.
FIELD 24-VOLT WIRING
FIELD 115-, 208/230-, 460-VOLT WIRING
FACTORY 24-VOLT WIRING
FACTORY 115-VOLT WIRING
1-STAGE
THERMOSTAT
Y R G
TERMINALS
CONDENSING
UNIT
Connect Y/Y2-terminal as shown for proper operation.
2. Some thermostats require a "C" terminal connection as shown.
3. If any of the original wire, as supplied, must be replaced, use
same type or equivalent wire.
5. The LED will flash the last stored fault code. Refer to the
Service Label (See Figure 14) to interpret the LED.
6. A component test sequence will follow.
7. Reinstall the Main/Control door.
Component Self−Test
NOTE: The furnace control component test allows all
components to run for a short time; except the gas valve and
humidifier terminal HUM 24 VAC are not energized. The EAC-1
terminal is energized when the blower is energized. The HUM
terminal is energized when the inducer is energized. This
feature helps diagnose a system problem in case of a
component failure. The component test feature will not operate
if any thermostat signal is present at the control and not until all
time delays are completed.
To begin Component Self−Test:
1. Remove blower access door.
2. Disconnect the thermostat R lead from furnace control.
3. Manually close blower door switch.
Gas Furnace: (F/G)9MXT
FIELD-SUPPLIED
FUSED DISCONNECT
208/230- OR
460-VOLT
THREE
PHASE
208/230-
VOLT
SINGLE
PHASE
GND
440 04 4321 08
A95236