49
TROUBLESHOOTING
If the furnace fails to operate check the following:
• Is the thermostat operating properly?
• Are the blower compartment door(s) in place?
• Is the furnace disconnect closed?
• Has the circuit breaker tripped or the control board fuse
burned open?
• Is the gas turned on?
• Are any manual reset switches open?
• Is the filter dirty or plugged?
• Is the flame sensor coated? (Remove and clean with
steel wool. (Do not use emery cloth or sandpaper!)
• Is there blockage in the condensate drain switch? Also
verify that there is no double trapping of condensate.
• Is the secondary heat exchanger free of debris and
clogs?
• Is evaporator coil clean and free of debris (If applicable).
• Are all the LED’s on the furnace control board constantly
ON? If not, refer to Table 13 or the wiring diagram, Figure
34 (page 32) or Figure 36 (page 34) to determine fault
condition.
• Are all the LED’s on the motor control board constantly
ON? If not, refer to Table 15 to determine fault condition.
IMPORTANT NOTE:
The furnace will lock out after 5 failed attempts for ignition
and will try again every hour if the call for heat remains.
• If the Inducer Blower is operating, and items above have
been verified, check the Blower Limit Switch and reset if
necessary. See Figure 47 (page 51) or Figure 48 (page
52) for component location.
• If the furnace operates when the Blower Limit Switch is
reset, contact a qualified service technician to identify
and repair the problem.
• If the furnace still doesn’t operate, check the Flame Roll-
out Switches and reset if necessary.
• If the furnace operates when the Flame Rollout Switch
is reset, contact a qualified service technician to identify
and repair the problem.
DIAGNOSTIC DESCRIPTION GREEN LED RED LED
Control Fault (No Power) Off Off
L1/Neutral Polarity Fault Flash Flash
1 Hour Lockout Alternating Flash
Normal Operation On On
Pressure Switch Closed Fault On Flash
Pressure Switch Open Fault Flash On
Open Limit Switch Fault Flash Off
DIAGNOSTIC DESCRIPTION YELLOW LED
Low Flame Sensor Signal Continuous Flash
Flame Present On
Table 13. Nordyne/UTEC Control Board Fault
Conditions
DIAGNOSTIC DESCRIPTION RED LED GREEN LED
Control Fault (No Power) Off Off
Normal Operation On On
Motor Fault On Flash
Twin Fault (No Motor Fault) Flash On
Communications Fault Flash Flash
Table 15. Motor Control Board Fault Conditions
RED LED
FLASH
ERROR/CONDITION
1 System Lockout (Retries Exceeded)
2 Pressure Switch Stuck Closed
3 Pressure Switch Stuck Open
4 Open High Temperature Limit Switch
5
Flame Sensed > 4.25 Seconds with Gas Valve
De-Energized
6 Open Flame RO Switch
8 Igniter Relay Fault
10 Open Fuse
11 Igniter Open
12 Inducer Relay Error
Flash codes NOT stored in memory
7 Low Flame Sense Signal
9 Twinning Fault
Off
Control Failure / No Power / Internal Fault / IRQ Loss
Gas Heating Lockout (Gas valve energized when it
should be de-energized)
Or Gas Valve De-energized when it should be
Energized
Rapid Flash Reverse Polarity
Continuous
On
Normal Operation
Table 14. Emerson Control Board Fault Conditions
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