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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 fi lter dirty or plugged?
• Is the fl ame sensor coated? (Remove and clean with
steel wool. Do not use emery cloth or sandpaper!)
• Are all the LED's on the furnace and motor control
boards constantly ON? If not, refer to Tables 3 - 4 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 verifi ed, check the Blower Limit Switch
(Figure 28, page 41) and reset if necessary.
• If the furnace operates when the Blower Limit Switch
is reset, contact a qualifi ed service technician to
identify and repair the problem.
• If the furnace still doesn't operate, check the Flame
Roll-out Switches (Figure 28) and reset if necessary.
• If the furnace operates when the Flame Rollout
Switch is reset, contact a qualifi ed service technician
to identify and repair the problem.
Diagnostic Description
Control Fault (No Power)
L1/Neutral Polarity Fault
1 Hour Lockout
Normal Operation
Pressure Switch Closed Fault
Pressure Switch Open Fault
Open Limit Switch Fault
Motor Fault
Diagnostic Description
Low Flame Sensor Signal
Flame Present
Table 3. Furnace Control Board Fault Conditions
Diagnostic
Description
Control Fault (No Power)
Normal Operation
Fixed
Speed
Motor Fault
Furnaces
Twin Fault (no motor fault)
Communications Fault
Control Fault (No Power)
Variable
Normal Operation
Speed
Motor Fault
Furnaces
Communications Fault
Table 4. Motor Control Board Fault Conditions
Green LED
Red LED
Off
Off
Flash
Flash
Alternating Flash
On
On
On
Flash
Flash
On
Flash
Off
On
Off
Yellow LED
Continuous Flash
On
Green
Red
LED
LED
Off
Off
On
On
On
Flash
Flash
On
Flash
Flash
Off
Off
On
On
On
Flash
Flash
Flash
27
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