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12. The circulating air blower will continue to run for the
selected Blower Off Delay(P5). This may be 60, 90,
or 120 seconds depending on the Jumper setting on
the Furnace Control Board.
Cooling Cycle
1. The thermostat calls for cooling by energizing the Y/Y2
or Y1 terminal with 24VAC.
2. The control energizes the blower in the cooling speed
and sends 24VAC to the contactor in the condensing
unit.
3. When the thermostat removes the call for cooling,
the contactor in the outdoor condensing unit is de-
energized and the control continues to run the fan for
a period of 60 seconds.
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!)
• 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).
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 6. Furnace 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
Fan Mode
• When the thermostat energizes the G terminal for
continuous fan (without calling for heat or cooling), the
indoor fan is energized on the selected FAN speed.
• If a call for cooling occurs during continuous fan, the
blower will switch over to the selected COOL speed.
• If the W terminal receives a call for heat during continuous
fan, the blower will de energize.
• A call for fan is ignored while in lockout.
• The blower will operate at 50% of the selected high
cooling speed for continuous fan operation.
• Are all the LED's on the furnace and motor control
boards constantly ON? If not, refer to Tables 6 - 7 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 40 or 41, page 51) 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 40 or 41) 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)
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 7. Motor Control Board Fault Conditions
Green
Red
LED
LED
Off
Off
On
On
On
Flash
Flash
On
Flash
Flash
Off
Off
On
On
On
Flash
Flash
Flash
29
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